Leisure hours among the gems

by Augustus C. Hamlin

THE OPAL.

What is the composition of this wonderful stone, which displays such wondrous hues? What is the nature of this remarkable mineral, which seems to concentrate within its substance all the glories of the rainbow, and which rivals in its hue the finest gem of the mineral world? The Turk believes that it falls from heaven in the lightning’s flash, and it is often regretted by the mineralogist that the theory cannot be sustained. Surely a gem so beautiful, so delicate and so pure ought to be of celestial origin, and free from the impurities and imperfections of the earth. Alas, we have but one precious stone that comes to us from the far-off region of celestial space,—olivine,—and that as yet has been found only in minute grains.

But if we cannot ascribe the origin of our beautiful gems directly to the stars and other bodies in space, we may affirm that their birth or development in the bosom of our earth may be due in a great measure to extra-terrestrial influences. And as regards the precious opal, if we cannot prove it of divine origin, we can with truth affirm that there is a deep mystery connected with the mineral both in its composition and its physical properties. The liberal-minded physicist to-day finds himself somewhat baffled when attempting to explain the phenomena of the gem in accordance with our imperfect knowledge of natural laws. Apparently it is nothing more than hydrated silica or quartz; but it is of a lower specific gravity, and some of its varieties are so tender and delicate in structure as to be at the caprice of the atmosphere.

It has been maintained that the peculiarities of the opal depend in a great measure upon the quantity of water it contained, and which, mixed mechanically with the silica, varies from three to twenty per cent. But some chemists who have interested themselves in the study of the composition of the mineral do not regard the presence of water as absolutely essential for the development of the varied flashes of color. We will only state in this brief sketch that there is certainly a mystery connected with the part water plays in producing and perfecting the beauty of the opal. This quantity or factor of water varies greatly in the different varieties of opal. Apparently when heat is applied to the mineral the brilliancy of its hues is increased, either from evaporation of its water or some structural change. But if the degree of heat is too great, or its application too prolonged, the hues of the opal vanish and cannot be recalled by human skill. The same results from the effects of heat may be noticed in other gems of greater density and hardness, as the emerald, the topaz, and the tourmaline. It has been maintained that a faded opal may be restored to beauty by immersion for a time in water, with the view of restoring the fancied loss by evaporation; but we fear that the experimentalist will be often disappointed with his results. However, there is one singular variety of the mineral known as the hydrophane, which does not exhibit colors until after it has been immersed for a time in water, and when removed from its bath and becomes dry again its hues vanish. Therefore, we may justly affirm that there is a mystery in connection with the influence of water in producing the color of the opal. The optical properties of this mineral do not afford decisive distinction, and it never crystallizes in regular and definite form like quartz, neither does it exhibit a trace of double refraction.

We will say no more at present concerning the composition of this interesting substance except to allude briefly to the experiment of Damour, who found the opal to turn black when sulphuric acid was applied to it; hence he inferred that the substance contained some organic matter, but precisely what he could not determine, although he suspected the presence of bituminous matter. Similar foreign bodies have been detected in many other precious stones. In fact, many of our gems are impaired by impurities; and so generally, that a stone of absolute purity is of rare occurrence. Even the diamond, which is regarded as the emblem of light and purity, is reckoned by microscopists as one of the foulest of gems.

Werner divided the opal into four sub-species, and Jameson has separated it into seven varieties. The principal divisions, however, may be classed as follows: precious or noble opal, presenting refulgent tints; fire opal, with fire-like reflections; girasole, with reddish reflections when exposed to the sunlight; common opal, translucent and without reflections; wood opal or petrified opal, possessing the characters of common opal; hyalite, clear and colorless as glass. There is another kind of opal which we have never seen, but which is described as the asteriated opal. We are not able to give a minute description of its appearance or draw a comparison between it and that of asteriated quartz, sapphire, or garnet. It is said to display great beams of light which undulate over its surface like the flashings of lightning piercing the storm cloud. The variety known as the moss opal sometimes displays in its interior dendritic crystallization of a dark substance resembling delicate mosses, ferns, or trees. And the gleam of the colored rays flashing amidst these miniature forests and groups of foliage often present charming effects.

The grand characteristic which gives to the gem its value and renown is the wonderful play of the colored reflections which it displays, and which embrace all of the prismatic tints of the solar spectrum. As we view its vivid rainbow flashes when the gem is held in the sunlight, we must admit it to be the most magnificent of gems, and join with the Latin philosopher, who remarked that it was made up of the glories of the most precious stones. For as the light falls upon it in varied directions, its reflections recall the lively green of the emerald, or the tender blue of the sapphire, the rich yellow of the topaz, or the gorgeous red of the ruby.

This mineral has not only been an object of delight to the fashionable world, but it has also been a wonder and a perplexity to the philosophers. In admiring its beauties and attempting to account for its phenomena, Newton was led to the series of experiments and to that train of sublime reasoning that gave to science the most brilliant and extraordinary of his discoveries. The colored refractions of the gem reminded the philosopher of the iridescence of the soap-bubble, and the soap-bubble suggested the undulatory theory of light. Newton, after long study of the opal, is said to have declared that its hues were produced by the refractions and reflections of light at the numerous minute fissures which traverse the stone in all directions. But this theory is denied by many at the present day, and especially by Mohrs, who maintains that the thin films of air filling the cavities of the stone would produce iridescence only. Other opticians believe the colored reflections to be due to laminæ formed by incipient crystallization, as seen in the equally remarkable mineral known as labradorite. Babinet believes the brilliant colors of the opal to be due to the narrow fissures in the stone, like those produced in the partial fracture of glass or quartz. He also refers for example to the colors of thin transparent plates, and believes that the colors of flowers are produced in like manner from the overlaying of the transparent tissues of which the petals are composed. This, then, according to the French philosopher, is the secret of the gorgeous hues of vegetation from their first development to the period of their final decay. The diamond, when cut in a regular form, displays the most magnificent flashes of the prismatic hues by artificial light; and although the mineral is composed of an infinite number of laminæ, no one maintains the theory that the color is produced by thin films of air like those in the soap-bubble. We also may observe the same hues sparkling among the dew-drops in the morning sunlight, and likewise in the artificial diamonds, which are composed of solid glass and apparently homogeneous.

In examining the interior of an opal, we often fail to perceive any cause for the reflections of color, especially in the limpid varieties. The flashes appear when the light enters the stone at a certain angle, but when viewed in any other direction the gem presents the usual appearance of common transparent quartz. In other varieties of the mineral, however, especially the milky or translucent, a cause for the colored reflections is easily observed. We have under observation the beautiful opal known as the “Oberon,” and beneath its translucent surface appear thin films of a faint reddish hue suspended at different depths within its interior. They are so well defined that their edges may be recognized, and they lie like thin clouds suspended in a hazy sky. But as the gem is turned so that the light strikes the film at a different angle, the scene is instantly changed, and a mass of flame replaces the sombre tint. It is a little curious that some of the films exhibit the different colors of the spectrum as the angle of light is changed, while others display only the green and blue color, no matter how the light strikes them. In fact, the films or patches, which are apparently alike, produce different results from the same rays of light; and some display the continuous spectrum, while others exhibit but one color. It is a little singular that all transparent minerals when fractured do not exhibit alike in their fractures the prismatic gleams displayed by quartz and glass. We have before us a beautiful transparent white crystal of adularia or moon-stone from St. Gothard, and although it is fissured and fractured in a thousand places, yet we observe little iridescence in it even when exposed to the sunlight.

The localities where the precious opal is now found are but few, and none of them were probably known to the ancients. All record of the old opal mines is now lost; but there were undoubtedly deposits of the mineral in Arabia, Syria, and in Asia, whence the ancients derived their gems. The famous Hungarian mines were not discovered until late in the fifteenth century, and the country was quite unknown to the Romans.

The principal mines explored at the present day, and whence most of our opals are now derived, are those of Hungary and Honduras. The Hungarian mines are of great extent and are now scientifically explored, but those of Central America are undetermined and but rudely mined. It is believed that there are other mines in Central America besides those of Honduras, for the natives at times bring fine specimens to the coast from localities widely separated. It is quite true that most of the opals of America are less hard than the Hungarian, but they are no less brilliant, and some of them withstand atmospheric effects and the wear of time quite as well. The Honduras opals are found near Gracias a Dios in porcelain earth, and are extracted in irregular masses, sometimes uniform or globular concretions, with rough and deeply indented surfaces. These masses do not exhibit the least tendency to crystallization like quartz, and they are generally quite small. Their natural colors are pale, and vary from brown to a pearly gray. They often exhibit a rich and varied play of the rainbow hues, even in their natural and rough condition. But sometimes, when this rough exterior is removed by the lapidary’s wheel, and the gem is highly polished, the colors vanish as if by magic. The polished stone no longer displays a single ray of the brilliant fires which illuminated every angle of the stone when in its rough state. This singular disappearance may be explained by the theory that the surface has been too highly polished, and the substance of the stone is rendered too transparent to permit the requisite degree of reflection, for when the surface is slightly roughened the play of colors again returns. The finest specimens are therefore those which are translucent, or those which, being transparent, are backed by an opaque ground which refracts the light.

The opal-bearing districts in Central America are far more extensive than is generally supposed. The Province of Honduras abounds in them, and we have evidence of others occurring in the State of Guatemala on the Pacific coast. The following descriptions of some of the opal mines of Honduras were published by Dr. J. Le Conte, in 1868, in his report of the Inter-oceanic Railroad survey:—

“Extensive beds of common opal and semi-opal are seen along a belt extending through the central part of the department of Gracias; but these varieties, though very beautiful and possessing high interest to the mineralogist, are without commercial value from the ease with which artificial products may be made which precisely resemble them. The localities worthy of exploration are those in which the opal forms veins (not beds) in compact but brittle trachyte of a dark color. The veins, as will be seen, are not confined to such rock, but seem to have their origin in it, and are probably not found except in connection with it. The best-known mines of precious opal are in the department of Gracias; several localities have yielded valuable gems, but they are all remote from the line of road. Some are in the vicinity of the town of Gracias, others near Intibucat; but the most important are at Erandique. The working is now carried on in a very small way; but the locality is extensive, and in my opinion mining on a large scale would be attended with profit. The country near by abounds with beds of common opal, as in many other places, but the gems occur in somewhat irregular veins running in a northeast and southwest direction, and with a nearly perpendicular dip. The veins are not continuous, but branch off and disappear at short intervals; neither are the contents of uniform quality, but the valuable parts are usually in belts in the vein, and limited on each side by portions of ordinary opal without play of colors. These lines of light are sometimes numerous and narrow, alternating with the common opal forming a very beautiful gem. Many again, even of large size, are uniform in structure, and exhibit a play of colors as brilliant as the finest opals from Hungary. The hill in which they are found is about two hundred and fifty feet high, and two or three miles in length, and for a width of half a mile for its whole length opals have been found wherever excavations have been made. The rock in which they occur is a hard, brittle trachyte of a vitreous lustre, and splintering into acute fragments when struck; a bed several feet in thickness overlying this rock is of a gray color and soft consistence, and also contains opal veins; it is probably a trachyte changed by atmospheric action.

“Other localities within two leagues of Erandique have furnished very fine opals, but as they are not now worked I did not visit them. Many places on the road between Intibucat and Las Piedras appear favorable to the existence of opal mines; but only careful scrutiny by a number of explorers can discover them. I would mention as most worthy of future attention the vicinity of Lepasale and of Yucusapa and the ascent of the great mountain of Santa Rosa. Greater expectations and indeed almost certain success will attend the search for opal mines in the valley leading from Tambla towards the pass of Guayoca, nearly on the line of the proposed road. Within half a mile of Tambla are immense beds of common opal of various shades of color. Near Guayoca are banded opals of alternate layers of opaque and semi-transparent white, having the appearance of onyx; these occur in a red vitreous trachyte and sometimes in contact with the masses of petrified wood which strew the ground for a considerable distance. Veins of a pearl-colored opal, with red reflections, are also found here; they have no commercial value, but serve as indications of better things in the neighborhood.

“Between the two localities mentioned (that near Tambla and that of Guayoca), Mr. W. W. Wright, chief assistant of the survey, has, by following some obscure indications, arrived at a vein of very pretty glassy opals and yellow fire opals, not of great value, but serving to strengthen the opinion expressed of the ultimate discovery of precious opals in the vicinity. Near Choluteca are found fire opals, some of which I was told possess merit. One (not of the best) given me is precisely similar to those obtained by Mr. Wright near Tambla. Within one league of Goascoran, as I am informed by Fernando Gaillardo, a resident of that town, is a mine producing opals with a good play of colors.”

Another remarkable deposit of opal was found by Mr. Wright about five miles east of Villa San Antonio in the plains of Camayagua. Though not of high value, it may be of use for ornamental purposes, being of a fine red color with transparent amethystine bands. It occurs in veins in gray porphyry, sometimes several inches thick, and may be procured in large quantities. Precious opal has been discovered in the iron mines at Barcoo in Queensland, and a number of specimens were exhibited at Philadelphia, at the Centennial. Some of these specimens were very fair, and gave promise of choice gems. The blue tints displayed by some of them were of great purity. They appeared to be of the hard variety, and therefore less liable to be affected by the ravages of time, or influence of exposure.

We will not fatigue our readers with a long dissertation on the formation of the opal. We will however, quote one theory which all may understand.

The boiling waters of the Iceland geyser are projected into the air at a considerable height, and are heavily charged with silica. As the waters fall upon the earth, large piles of earthy and stony material are formed in process of time. When these silicious masses are broken open, translucent and transparent portions of silica are found, exhibiting the colored reflections of the noble opal as long as they remain hydrated, or, in other words, as long as they retain a certain quantity of water in their composition. This observation has led M. Descloizeaux to the belief that opals found in volcanic rocks or igneous rocks have had their origin in phenomena analogous to those of the Iceland geysers. The matrix of the opal is a varied one. The gem is not only found in porcelain earth, but it occurs in fissures and seams, in what appear to be old igneous rocks. It has also been deposited in recent periods, as in the limestones of the argillaceous beds, and even in the formations of the silicious waters of the hot springs of the present time. The decomposed cement of the old Roman ruins around the hot springs of Polombieres, uniting with certain chemical properties of the waters, has changed into opal and hyalite. Trees within historic times have been transformed into opal or semi-opal; and on the island of Unja one may see blocks and trunks of trees (some even showing the marks of the hatchet) converted into opal. Silicified trees forty or fifty feet in length, may be seen stretched from Cairo to Suez. In many other parts of the world trees and plants have been transformed by the mysterious processes of nature into a silicious substance possessing the characters of opal; but none of these vegetable metamorphoses exhibit the rainbow hues to any marked degree. Quartz, when flawed in the interior, sometimes exhibits a remarkable iridescence, and may imitate the opal, especially if viewed at a distance. Such specimens of iridized quartz are called “iris,” and they may be artificially produced by a sudden blow upon the stone, or by heating it and suddenly dropping it into cold water. The superb iris ornaments worn by the Empress Josephine were of remarkable brilliancy and play of colors. In ancient and mediæval times, iridescent quartz was held in great esteem; and fine specimens mounted in antique jewelry are preserved at the present day. It is described in the “Lapidarium” of Marbodeus as follows:—

“By the Red Sea the swarthy Arabs glean
The iris, splendent with the crystal’s sheen;
Its form six-sided, full of heaven’s own light,
Has justly gained the name of rainbow bright.”

The fire opal occurs in its greatest perfection in the porphyritic rocks at Zimapan in Mexico. It is generally of a translucent hyacinth-red color and flashes forth dazzling beams of fiery carmine-red with yellow and green reflections. This Mexican gem is the most beautiful and gorgeous of all the varieties of opal; but, alas! it is also the most sensitive, and is frequently irreparably injured by water or exposure, or even by sudden atmospheric changes. So easily affected are the opals by the vicissitudes of the weather that they are almost always brighter in summer than in winter. But there are some varieties that are not so easily influenced, and are not injured by contact with water. The fact that this variety of opal is injured in course of time by contact with moisture or careless exposure is not remarkable when some of the harder gems undergo a change from similar exposure. The hard amethystine quartz, when worn as a finger ornament, will completely bleach out and become colorless in a few years. The black opal is the product of art, and for this purpose harlequin opals are used. The harlequin opal is simply the matrix of other gems spotted here and there with flakes of color dispersed over an opaque ground, and its name was suggested by the resemblance to the motley tints of the harlequin’s dress. Masses of the matrix, with fragments or specks of opal interspersed in its substance, are soaked for a time in a saccharine solution, and afterwards in diluted sulphuric acid. The porous parts of the matrix absorb a minute quantity of the solution, which is afterwards charred by the sulphuric acid; while the solid and transparent parts remain unchanged and exhibit an increased play of colors upon the black ground.

The ancients undoubtedly obtained their opals from Syria and Arabia or other Eastern countries, for the Hungarian mines which now supply the world with most of the finest gems were not discovered until the fifteenth century. The famous mines are situated on a mountain which is one of the spurs of the Carpathians. They belong to the Seignory Peklin, and are near the village of Czernizka. In the early days of their discovery, and for a long period afterwards, they were explored casually and from time to time. At the present day, however, the explorations are conducted with regularity and the appliances of skilled labor. The surface of the mountain has been removed to a great extent during this long-continued search of many centuries, but as yet no explorations have been attempted into the interior of the ledges. The true matrix appears not to be more than four to eight yards in depth below the alluvial soil. It is arranged in continuous beds of little hardness, but resembling porphyry in color. The opal formation appears to extend to a considerable distance beyond the flanks of the mountain; for, in the cultivated fields below, the laborers often find beautiful gems washed out by violent rain-storms from the exposed and superficial soils.

The opals from these mines are the hardest and most enduring of all the known localities of the earth, yet they have to be carefully tempered to heat and moisture before they can be utilized. M. Frangoll Delius, the Commissioner of the Austrian mines, states that these opals, when first extracted from their rocky beds, are soft, friable, and tender, and not in a condition to be worked. But after they have been exposed to the air and sunlight for some days or a definite time, they become harder, and the stones also become decidedly smaller from contraction. This exposure is required to be carefully regulated lest the stone become fissured by sudden contraction. When exposed to the effects of artificial heat, colors appear sooner than when it is submitted to the action of the sun’s rays. It is curious to watch the gradual unfolding and the display of these beautiful hues. At first the stone is limpid and rayless as pellucid quartz. But as the quarry water is evaporated by the effect of heat or time, and the stone contracts in volume, the iridized reflections then begin to appear, increasing in perfection and variety, until the requisite degree of moisture is expelled. If this evaporation is carried too far by heat the splendors of the gem vanish completely, never to be recalled. It is a singular fact that exposure to the sun’s rays gives the opal much finer hues than the action of artificial heat. And it is also a remarkable circumstance that of all the variety of prismatic hues displayed by this gem, the violet invariably appears the first, according to M. Delius.

The ancients rarely engraved upon the opal, influenced perhaps partly from its enormous value in those times, and partly from its soft and fragile nature. They imitated the gem, however, with such perfection that Pliny declared that it was almost impossible to distinguish the false from the real. Modern gem imitators have utterly failed in producing anything approaching the precious opal in beauty. The assertion of Pliny in regard to the imitation of the glories of this gem has always been received with incredulity by the moderns on account of the failures of our most skilled artisans; but the discoveries among the ancient Phœnician tombs in the island of Cyprus by Di Cesnola rather strengthen Pliny’s remark.

In this collection we may view a great and elegant variety of glass-ware exhumed from the tombs of the Phœnician nobility who lived three thousand years ago or more. Many of these vessels gleam with what appear to be iridescent tints of gold, blue, red, and other colors of the loveliest tints, recalling to mind the most beautiful and gorgeous reflections of the opal. Some of the articles are entirely of one color, while others are composed of patches of various hues resembling enormous opals with broad gleams of pure color. Peligot maintains that these superb colors are clue to the effect of great age; and the substance of the glass being separated into laminæ, the colors may be explained by the law of iridescence. But we are half inclined to believe that they may be due to the skill of the artisan in a great measure,—hence the variety of color in different vessels of the same age. In the famous collection of Signor Castellani there is a solid glass ring quite two inches in diameter taken from the ancient Etruscan tombs. This interesting relic exhibits patches of color as bright as the prismatic gleams, and they do not appear to arise from any disintegration of the material, but rather to be produced by the design of the workman. We surely will not ascribe to effect of age the decided iridescent glaze which we see in the Maiolica pottery of Hispano-Moresque objects of the thirteenth or fifteenth centuries, or in the Gubbio products of the sixteenth century.

The famous opal of history was that which was worn in a ring by the Roman Senator Nonius in the days of the Triumvirate. Its size scarcely exceeded that of a hazel-nut, yet its beauty and perfection were such that it was considered a marvel among the dilettanti of Rome, and valued at the enormous sum of nearly a million dollars. Marc Antony, remembering the sacrifice of the matchless pearl by Cleopatra, and still enslaved by her irresistible charms, sought to obtain the opal, intending it as a present to the siren queen of Egypt. But Nonius refused to part with the treasure which was the idol of his heart, and sought safety in flight. The beauty and charm of the gem may be estimated by the fact that banishment then to a Roman was worse than death. History makes no further mention of this wonderful opal, and even if preserved among the spoils of ancient Byzantium its glories have probably vanished ere this, yielding to the destructive effects of time.

The finest opal of modern times was that which was worn by the Empress Josephine in the days of Imperial splendor. It was indeed a magnificent gem. Its flashing beams of light were so strong and vivid as to give the appearance of living flames of fire, and hence the name of l’incendie de Troie,—“the burning of Troy,”—was bestowed upon it. The base of this opal was completely opaque, but the superior portion was perfectly transparent, and through it were reflected a multitude of fiery gleams of red light. The fate of this beautiful gem is unknown. There are two splendid opals still to be seen among the Crown jewels of France, notwithstanding the frequent change of dynasties. One is placed in the centre of the Order of the Toison d’Or, and the other forms the clasp of the royal mantle.

In the imperial cabinet at Vienna is exhibited the grandest specimen of this gem yet discovered. It was found in the mines of Hungary in 1770, and purchased by the Austrian Government. It measures 3³⁄₄ inches in length, and is 2¹⁄₂ inches in thickness. Its weight is about seventeen ounces, and its value is estimated at about $300,000. Although it is injured by several cracks and fissures, it possesses a brilliant play of color, and is justly regarded as the finest specimen known, even surpassing the beautiful fire opal brought home from Mexico by Humboldt, and which is still preserved in the museum at Berlin.

At the close of the last century, but before the Revolution broke out in France, Mons. D’Auguy, a financier of Paris, came in possession of a most remarkable opal of the harlequin variety. It was of oval form, ⁷⁄₈ of an inch in length by ⁵⁄₈ in breadth. This gem was of wondrous beauty, and was pronounced perfect by the connoisseurs. It is now in the hands of the family of Count Waliski. At the same time the well-known amateur Fleury owned a rival to Auguy’s opal, which it exceeded slightly in size.

Another magnificent opal is described by Jackson as having been exhibited at Vienna. It was nearly an inch in length, and was of the harlequin order, having three longitudinal bands from which flashed resplendent flames of light and color. It was pronounced by the virtuosi of Dresden and Vienna to be the third in rank of all the fine opals then known.

In the Musée de Minéralogie of Paris may be seen a splendid opal which has been carved into a bust of Louis XIII. when a child. King very properly exclaims against the barbarism and extravagance where work and material mutually destroy each other’s beauty and value. The Spanish historians, in their marvellous stories of the wonders seen in Mexico at the time of the Conquest, describe the image of the mystic deity Quetzalcoatl (God of the air) on the great pyramid of Cholula, as wearing a mitre waving with plumes of fire, and which was supposed to have been produced by masses of the fire opal.

Dr. Le Conte brought home from his geological surveys in Honduras, a number of beautiful opals from the mines in that country. They have since been cut and mounted in gold with diamond settings, in the form of a necklace, which is regarded by connoisseurs as one of the most valuable jewels in the United States.

At the Centennial Exhibition of the United States, Austria exhibited some very beautiful opals of various kinds, both polished and in the natural state. One of the polished gems was two inches in diameter and valued at $25,000. It was of a faint milky white tint, like most of the Hungarian opals, and displayed a charming arrangement of colors.

The splendors of the opal are best seen when exposed to the direct rays of the sun, and viewed through a magnifying glass of low power. The dazzling scene has no equal in art or nature, for the vivid hues of the solar spectrum are here displayed with the most charming effect. The colors are in broad patches and not blended with their complementary hues as seen in the continuous spectrum, and the effects of the pure green, red, blue, and yellow, flashing forth in perfect purity and intensity, without definite arrangement, remind the observer of the brilliancy of the kaleidoscope. In this fascinating display of hues one might expect to see the colors pass into each other as in the solar spectrum, and as the field of view is changed; but such is not always the result. The red may exhibit a tinge of yellow, or the green a shade of blue before they disappear from view; but generally the patch of color ends abruptly, preserving its purity of tint to the last.

The alternate and irregular flashing of all these varied hues always presents a harmonious spectacle, such is the wondrous power of Nature in all her arrangements and groupings. The stone, when arranged by the art of the lapidary, is almost always cut with a convex surface. However, when the opal is attached to an opaque substance which serves as a reflector to the rays of light, the stone may then have its surface cut almost flat. The colors displayed by this gem embrace quite all of the tints seen in the solar spectrum, and they are as pure. The shades of green, blue, yellow, and red will bear comparison with the hues of the solar spectrum, and the gems of other minerals are rare that can bear this decisive test. Sometimes but one color is visible in the stone, and then it is called emerald or golden opal, according to the tint exhibited.

The purchase of opals in the rough natural state is attended with danger, for often the glittering mass, after being shaped and polished by the lapidary, is transformed into a transparent but hueless stone. The cutting of the opal is always a hazardous operation, from the fragility of the material and the special tact required in determining the shape to be given the gem. We will relate an instance to illustrate the history of the whole.

A traveller from Central America brought home a splendid rough fire opal which dazzled the eye with its fiery reflections. We took it to an honest lapidary, who received it with a doubtful look. The next day the opal was returned, having been shaped into the usual oval form, but only a faint gleam of any of the colored rays flashed from its surface, or the interior. “Is this the gem we gave you yesterday?” we demanded of the artisan. With a smile the lapidary took the transparent stone and roughened its finely polished surface upon the wooden wheel. In an instant the lost fire returned as if directed by magic’s wand. The perfect transparency of the gem, with its high polish, had allowed the rays of light to pass directly through it, and there was but little refraction, but on roughening the surface the light was interrupted and the peculiar property of the mineral displayed. Unfortunately the lesson was not concluded here. At the last touch of the wheel the beautiful gem flew into two parts, and its glories departed in an instant. Saddened with the day’s experience, we took the two fragments, cemented them together, and tossed the stone into a drawer which contained other mineral specimens of no great value. Some months after, while searching for a misplaced mineral, a gleam of light suddenly flashed out as we opened the drawer. It was the neglected and abused opal, which now gleamed with the energy of a living coal of fire. It had recovered its beautiful reflections, and still adorns, notwithstanding its fracture, a most cherished jewel.

Whence this mysterious change? the reader may ask. We can only say that the complete transparency of the stone had been lessened, and perhaps the change was due to the action of some of the ingredients of the cement with which we united the fragments of the broken gem.

Some of the Central American opals have the reputation of fading and becoming translucent and opaque in course of time, or according to the circumstances of exposure. We will relate an instance which forms a part of our experience and education in the study of gems.

A few years ago, two Spaniards arrived in New York with a bag of rough opals brought from Central America, but from what particular locality we never learned. The specimens varied in size from that of a bean to that of an English walnut, and were extremely beautiful. They had a fresh appearance, as though they had been recently extracted from the mines, and many of them had portions of the soft sandy matrix still attached to them. They excited suspicions of not having been properly tempered and hardened by exposure; but their beauty, which reminded one of the perfect glow-worm, or lumps of phosphorus moistened with oil, did not allow the spectator to hesitate about the purchase of them, especially as they were offered at a moderate price. We invested in the purchase of several charming specimens, and never wearied in examining their exquisite effects. Still, we felt a vague suspicion of the enduring qualities of our newly acquired treasures. The most beautiful stone, the size of a small almond, we carried in our pocket for a long time, not only for our gratification but for the purpose of studying the effect of the atmosphere upon its reflections. Soon after our acquisition, we fancied a slight shadow or nebulosity appearing in one end of the stone. We carefully watched it, and before long an indistinct cloudiness began to appear, like the dim and distant haze of a summer sky on the commencement of a storm. Even then we thought it might be mere fancy on our part. But when the shadow changed to opacity, and the transparency of the gem, with its beautiful reflections, vanished, never to return, we were compelled to admit that even substances of the mineral kingdom had their diseases as well as forms of the organic world.

This is indeed but one example to illustrate a theory; but most of those we purchased at that time of the Spaniards have altered in appearance, and some of them quite as seriously. Therefore we have arrived at the conclusion that recently mined opals should be bought with caution; and that the perfection of a rough opal as a gem cannot be safely estimated until after it has been cut by the lapidary.

No definite idea can be given in relation to the price of the opal, so much depends upon the degree of its brilliancy and play of colors. The gem is not sold by weight, but its value is estimated by its size and the perfection of its charms. An opal half an inch in diameter exhibiting fair colors may be worth $5, and another of the same size, of greater perfection, may bring $5,000, or more. The palmy days of the opal were during the period of Roman luxury, as the beauties of the diamond were not then fully revealed, and the opal flashed forth its marvellous beams of color both by daylight and artificial light. The gem then commanded enormous prices. According to the tables of Dureau de la Malle, the opal of Nonius was valued at twenty million sesterces, or about eight hundred thousand dollars. Enormous as this sum of money appears, Catherine of Russia would have given as much for the gem, if its beauty had been in keeping with its reputation.

The commerce of the opal affords a curious example of credulity and superstition, which is in singular contrast with the progressive ideas of our advanced civilization. In times past the changes that sometimes occur in the opal from physical causes have impressed the minds of some excessively superstitious people as due to supernatural causes. And from these trivial fancies the most beautiful and recherché of all that Nature has offered to us in the mineral kingdom has been placed under ban. This superstitious dread may be of ancient origin, and whence its source we know not. But it is a matter of history that the opal was the favorite gem among the Romans in their best periods of intelligence and refinement. So far from being feared at that time, it was eagerly sought for, as it was supposed to possess the power of warning against disaster, and exhibiting the rosy herald of joy. Hence it has been thought that a feeling of superstition as well as of avarice influenced Nonius when his paragon was demanded of him.

It is possible that the dread of the opal may be derived from the superstitious fancies that have descended to us from neolithic times, like the superstitions connected with the ancient stone implements which are now called in Western Europe elf-stones. In Scotland at the present day the ancient arrow-heads of stone are known as elf-bolts or fairy shots, and believed to protect the wearer from disease or misfortune. Thus it appears that stone weapons of an extinct race are used as ridiculous charms by later nations far advanced in civilization. History shows us how elves and fairies were created in the popular imagination from neolithic sources, and how weapons and ornaments of stone, amber, and metal became invested with mystic powers as objects of handicraft of the elves themselves. These objects are not only regarded as fairy charms among the races of the East, but the belief in their powers and use is quite as strong and tenacious among the Celtic portions of Europe. In other countries these primitive ideas of fairies and charms have become modified, and blossomed into poetic fancies to please chiefly the innocence of childhood. Some of these the genius of Shakspeare and other poets have made beautiful, and to these we offer no objection. Poetic license may sometimes invest an object with a positive effect which eventually may assume the appearance of fact. Thus the allusion to changes in the beauty of the opal in connection with misfortune, which was made by Sir Walter Scott, in his novel “Anne of Geierstein,” was taken to heart seriously by many of his readers, and the gem was placed under ban. The popular imagination became so strongly affected that the commerce of the opal in England became very seriously injured; and even at the present day many a timid maiden hesitates over the selection of the opal for ornamentation. Every mineralogist and man of science will rejoice to learn that Queen Victoria exhibits sterling good sense in selecting the opal among her choicest family gifts, thereby presenting a pleasing contrast to the superstitious and foolish fancies of the Empress Eugénie.

To the amateur who loves the rare and beautiful, with a feeling untrammelled by any of the misty traditions of the past or the caprices of fashion of the present, the opal is the dearest of all the gems. For it is not only rare, but it displays the glories of all the other gems; and it is the only one that defies the skill of the modern artisan to imitate. Its flash instantly betrays its character, and places it above suspicion, while quite all of the precious stones regarded as gems are now imitated so perfectly as to require close and careful inspection, and sometimes the application of scientific tests.

When we recall the phenomena of the opal, and the wonders of its reflections, with their strange and sudden disappearance, we may pardon the credulity of the Arabian romance writers in ascribing to the gem supernatural powers. It was a beautiful theory with them that it falls from heaven in the lightning’s flash, and is the veritable Ceraunia. Its charming and mysterious play of colors suggested to their ardent imaginations the glories of Paradise, and hence they invested it with wonderful talismanic properties, and believed it to be the abode of afreets and genii. Alas for romance! Science clearly demonstrates that many of the phenomena which puzzle the superstitious are simply due to atmospheric influences and to the natural laws which regulate the decay of organic and inorganic forms.