The occurrence of fluid cavities in quartz, chalcedony, sapphire, and other minerals, is due at times to cavernous structures formed during the growth of these minerals, when the crystalline substances, for some reason, instead of filling these up solid, will avoid the caverns and enclose the liquid of crystallization. In agate inclusions this is found with silicious content, possibly due to the fact that it is to an extent carbonic acid gas, or water containing salt or some other foreign substance. In agate chalcedony, whether in pebbles as minute as a pinhead, or in amygdules several feet across, the liquid is enclosed because the walls of the gas-pores in the rock, which are frequently almond-shaped, are gradually becoming smaller, or rather the walls thicken by the deposition of the silica forming agate, chalcedony, or any impenetrable layers, or else an impenetrable form of quartz; then again, frequently toward the centre or when the liquid forms less rapidly, or through some change, the quartz becomes crystalline, either colorless, smoky, or amethystine, and this is due to various inclusions. This gradual thickening of the walls means that the aperture into which the liquid penetrates becomes smaller and smaller until at last it is entirely sealed, so that it becomes enclosed in a kind of nature’s water-bottle, these being sometimes as large as in the chalcedony specimens from Uruguay; this is also the case with the hydrolites and the enhydros, when they can be shaken and the water rattles as in a bottle.
An occasional small Redondo Beach, California, or Medford, Oregon pebble contains a moving bubble of air in liquid.
Most wonderful specimens of rutilated quartz are the great, rich brown, possibly titanium-colored masses in the Morgan Collection at the American Museum of Natural History, that in the Vaux Collection at the Philadelphia Academy of Natural Sciences, and a smaller mass in the British Museum; these were all obtained near Middlesex, Vermont. The rutile is a rich transparent or translucent red, varying in thinness from that of an ordinary needle to that of a knitting-needle, and even to that of a thin lead-pencil. Wonderful specimens are also found in the Alps of St. Gotthard, in Madagascar, and in Alexander County, North Carolina, where they are found in quantity as minute crystals of a rich red or golden yellow.
Other curious and interesting rock-crystals with inclusions are those showing enclosed drops of water, the kind termed enhydros by Pliny[[51]] and many old writers; in some of the rarer specimens the enclosed water is present in considerable quantity. Quartz with inclusions of this type was highly appreciated in the Greco-Roman world, and one of the best poets of the Decadence, Claudian (fl. about 400 A.D.), composed a series of poetic epigrams upon them, seven of these being in Latin and two in Greek. An example of the best in each tongue, the first in the former and the second in the latter, must be of interest, although the literal prose version cannot have the charm of the original verse.[[52]]
The Alpine ice, already precious in its frigidity, acquires an intense hardness through the action of the solar rays, but unable to transform itself entirely into a gem, it betrays its original source by the water that still remains within it. This adds at once to the beauty of this liquid stone and to its value.
In its changeful aspect, this crystal born from snow and fashioned by the hand of man is an image of the world, of the heavens enclosing cruel ocean in their wide embrace.
An old superstition among the Laplanders of Sweden is that in order to avert or cure disease which may be or has been caused by sleeping in the open air on the exposed moorland, three pebbles should be gathered, one from the water, one out of the earth, and the third from the surface of the ground or “from the air.” These are placed on a fire until they become red-hot, and are then thrown into water; the stone which sizzles most is that belonging to the element which has caused the illness. The whole body, or sometimes only the afflicted part, is to be moistened with the water in which the pebbles have been immersed, and each separate stone is to be carefully returned to the spot whence it was taken.[[53]]
Near Middleville, in Herkimer County, New York, in a calciferous limestone, gray and brownish-gray in color, there are numerous cavities varying in size from that of a pinhead to that of a man’s head. In these cavities are found carbonaceous substances such as asphaltum and other hard, black hydrocarbons. These cavities also frequently show mud or sand adhering to the sides, or mud and sand mixed with the petroleum, in which are often found brilliant and transparent rock-crystals, the purest of any found in the world. They are unusually perfect hexagonal prisms with both sets of six pyramid faces; that is, with same slight modification, eighteen brilliantly polished faces. These are especially sought after on account of their great purity, and because it is considered that he who wears one will have fair weather and secure the blessing of fair sailing on the sea of life. Some of these crystals are so small, though of absolute perfection, that it would require 250,000 of them to weigh an ounce; others again are sometimes as large as from one to two inches in length. When not entirely transparent they frequently contain inclusions of black asphaltum or other hydrocarbons and also contain hollow cavities which are filled with fluid, sometimes salt water and sometimes liquid carbonic acid gas. In these are moving bubbles and occasionally a heavy hydrocarbon; that is, a bubble will ascend and the hydrocarbon will sink; or else the bubble will rise and take with it a small speck of hydrocarbon, and another will sink. In a wonderful specimen now at the American Museum of Natural History there is an object like a small spider of hydrocarbon which sinks while a minute water-bubble rises. They are called fair-weather stones.
Tasmanian rain-makers use white stones in their magical rites; however, the stone by itself is not considered an effective talisman, for it must be dipped in the blood of a young girl to give it added power. After a number of white pebbles have been steeped for a time in this blood, the rain-maker ties them up in strips of bark and sinks them in some deep water-hole in which a diabolical spirit is supposed to dwell. The natives confidently assert that this ceremony is soon followed by the desired rainfall. As the belief prevails here as elsewhere, that these white stones or pebbles to retain their power must not be looked upon by a woman, it seems a little strange that the rain-bringing stone is dipped in a young girl’s blood.[[54]]
However, white stones have not always and everywhere been regarded as lucky, for it is stated that among the fishermen of the Isle of Man the presence of a white stone in a fishing-smack is confidently believed to portend poor fishing. Indeed it has been reported by a Scotchman, who went out in a fishing boat for several consecutive days with a party of Manx fishermen, that after a succession of days marked by poor fishing they began to nickname him “White Stone.”[[55]]