To carry out a regular system of investigation among quartz reefs, mineral veins, and metalliferous rocks, certain tools and appliances will be needed—picks of Cornish pattern, such as is represented in the above [illustration], sets of steel borers, with cockscomb ends, sets of steel gads or wedges, borer, steel and gad steel in bars, blasting powder, safety match in coils, some heavy hammers, a portable forge (such as is [here represented]), set of smith’s tools, shovel blades, spare pick-heads, and hilts of ash, &c. When it is deemed requisite to blast a portion of rock, the borer and hammer are used much as shown in the [annexed illustration]. One man, sitting on the ground, holds the borer upright and turns it freely round, whilst his assistant strikes it with the hammer. A little water dropped from time to time down the hole keeps the bit cool, and facilitates the operation. As sludge collects, it is removed with a species of scraper, fashioned from the end of an iron bar. A small rod or stick, with its end fibres frayed and set up like a mop, is used for drying out the hole. Should it be in wet ground, where moisture remains in spite of swabbing out, a cartridge composed of tallowed cotton or oiled paper, may be used to inclose the powder in. According to the old-fashioned plan, which some miners still follow, a long pointed copper rod or needle was pressed into the charge after it had been rammed into the bottom of the hole. Round this rod clay, pulverised clay, slate, &c., was closely packed, and driven with a copper tamping rod until the hole was compactly filled up. The needle was now withdrawn, and a match, composed of a long marsh reed filled with mealed powder, thrust down the orifice until the charge was reached, when the upper end was held in its place by clay. A bit of rag, smeared with moistened powder, was attached to the head of the reed, which, when fired, burned long enough to afford time for the miners to shelter themselves from the effects of the explosion. Since the introduction of the so-called patent safety match, it has been with great advantage substituted for the reed; the burning of this match or fuse is generally so uniform, that it has only to be cut according to the distance between the hole and the place of shelter. Even this great improvement in the means of ignition falls very short of exploding by voltaic electricity, which should always, when practicable, be had recourse to. The wandering miner and explorer will, however, seldom be able to avail himself of its valuable aid, or the use of gun cotton or nitrate of glycerine, which agents have of late been much lauded as substitutes for gunpowder in mining operations.
It not unfrequently happens that diamonds and other precious stones are found in river beds, and such other localities as miners are in the habit of examining. We therefore offer a few hints and directions for the identification of these in their rough state, as given by Professor Tennant:
Precious stones, to identify.
“Fig. 1 is an octahedron; Fig. 2 an octahedron having six planes on the edges; Fig. 3, dodecahedron with rhombic faces; Figs. 4, 5, and 6 are rarer forms. Out of 1000 diamonds I have generally found about one of the form of Fig. 6; about ten like Fig. 5; fifty like Fig. 4; and the remainder like 1, 2, 3, in about an equal proportion. With regard to the size and weight of diamonds, 500 out of 1000 which came in the same parcel were found smaller than Fig. 1, which is the exact size of a diamond weighing half a carat; 300 were of the size 3, 4, 5, and 6—none of these exceeded a carat in weight; eighty of the size 2 weighed a carat and a half; only one was as large as Fig. 16—this weighed 24 carats. The remainder varied from 2 to 20 carats, a carat being equal to three grains and one-sixth troy. Fig. 7 consists of a conglomerated mass of quartz pebbles rounded through having been water-worn, a crystal of diamond, the size of a small pea, and various grains of gold, the whole cemented together by oxide of iron. This specimen is peculiarly interesting at the present time, as showing the association of diamonds with gold. In 1844 a slave was searching for gold in the bed of a river in the province of Bahia, and discovered diamonds. It being a new locality for diamonds, 297,000 carats were collected in two years, which produced upwards of 300,000l. I see no reason why diamonds should not be found in Australia, Canada, California, as well as in those other gold districts from which they have hitherto been obtained. The value of the most inferior diamonds, unfit for jewellery, is 50l. per ounce. Could they be found in sufficient abundance to be sold at 5l. per ounce, the benefit to the arts would be incalculable. Not only would the seal engraver, watchmaker, lapidary, glazier, &c., be able to procure them at easier prices, but numerous substances would be rendered useful which at present cannot be profitably worked owing to the high price of diamonds.
“Figs. 8 to 11 represent four crystals of corundum. This substance is commonly found in six-sided prismatic crystals, and frequently terminated at each end by six-sided pyramids. When transparent, and of a blue colour, it is known in jewellery as the sapphire; when merely of a red colour, it is called Oriental ruby; and when this colour is of a rich depth, the stone is more valuable than even the diamond.
“Figs. 12 to 14. Three crystals of spinel-ruby. It is of various shades of red, and is easily distinguished from corundum by the peculiarity of its crystalline form and inferior hardness.
“Figs. 15 and 16. Crystals of garnet. These are chiefly found in the form of the rhombic dodecahedron; are occasionally of a beautiful red colour; when semi-transparent, are called by the jewellers “carbuncles.” They are of comparatively little value.
“Figs. 17 and 18. Two rhombic prisms of topaz. It is found in rivers, frequently with all the edges and angles of the original crystal worn off, and presenting a round appearance, in which state it is often mistaken for the diamond, owing to the colour and specific gravity of each being the same. It may, however, easily be distinguished from it by the difference of the hardness and fracture. The diamond yields readily to mechanical division parallel to all the planes of the regular octahedron, the topaz only at right angles to the axis of the crystal.
“Fig. 20. Tourmaline. A crystal having six sides, deeply striated in the longitudinal direction, and terminated by a three-sided pyramid; colour varying from black to brown and green. Transparent specimens are useful to the philosopher in experiments on polarised light.