A Manual of Mineralogy

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Longman, 1814 - Mineralogy - 164 pages
 

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Page 68 - ... the minuteness of the crystals, has not been detected. It occurs also in crystalline grains, either aggregated, solitary, or disseminated. It yields to the knife, and is brittle; specific gravity 5.7 — 6.1. Exposed to the blow-pipe, it melts before ignition, and, on increasing the* heat, it burns with a greenish flame, and is almost entirely volatilized in a dense white vapor, with a pungent, acrid odor, like that of horse-radish.
Page xlii - ... throat. When this has been acquired, the blowpipe may be put into the mouth and the confined air expelled through the pipe by means of the muscles of the cheeks : as soon as the air is nearly exhausted, the expiration from the lungs instead of being made through the nostrils is to be forced into the cavity of the mouth ; the communication is then instantly to be shut again by the tongue, and the remainder of the expiration is to be expelled through the nostrils. The second and all subsequent...
Page vii - ... immediately applied. In common language hardness and refractoriness are often confounded. A stone that endures many heavy blows before it gives way is considered as harder than another which requires fewer blows for its fracture. The most unexceptionable method of ascertaining the hardness of a mineral is the greater or less ease with which it yields to the point or edge of a knife of hardened steel. The whole range of hardness obtained by the use of this instrument may be conveniently divided...
Page lv - ... abilities and whatever be his industry, must long feel his inferiority to one who has been educated in a regular school of the science, enjoying the advantage not only of books, but of living instructors, of well furnished cabinets, and of that encouragement and emulation which can only be duly excited, in scientific as well as in other pursuits, by the support of companions and the opposition of rivals. Under these circumstances it becomes very desirable that some new attempt should be made...
Page xlii - ... mouth, and the confined air expelled through the tube by means of the muscles of the cheek. As soon as the air is nearly exhausted, the expiration from the lungs, instead of being made entirely through the nostrils, is to be partly forced into the cavity of the mouth : all subsequent supplies of air are to be introduced in the same manner as the first. Thus, with a little practice, the power may be obtained of keeping up a continued blast for as many minutes as may be necessary for any ordinary...
Page 46 - Before the blowpipe on charcoal, it usually decrepitates, then melts, and on cooling forms a polyhedral globule, the faces of which present concentric polygons ; if this globule be pulverized, and mixed with borax, it melts into a milk-white enamel, which, on continuing, the bead becomes transparent, the lower part being studded with globules of metallic lead.
Page 32 - It tinges the flame of the blow-pipe of a bright green and blue, muriatic acid rises in vapours, and a bead of copper remains on the charcoal.
Page 29 - ... but is very difficultly fusible : it gives a dirty green colour to borax. 487. Emerald Copper, Dioptase, Silicate of Copper — Emerald green; crystallized in elongated rhombic dodecahedrons; semi-transparent; lustre shining, pearly ; scratches glass feebly ; brittle ; frangible. Sp. gr. 3-3. — Before the blowpipe, it becomes of a chesnut brown, and tinges the flame green, but is infusible ; with borax it gives a bead of copper. 488. Blue Copper Ore, Blue Carbonate of Copper, Mountain Blue,...
Page xlii - ... to accomplish which, the first thing to be done is to acquire the habit of breathing easily, and without fatigue, through the nostrils alone, while the mouth is filled and the cheeks inflated with air ; when this is acquired, the Blowpipe may be put into the mouth, and the confined air expelled through the tube by means of the muscles of the cheek. As soon as the air is nearly exhausted, the expiration from the lungs, instead of being made entirely through the nostrils, is to be partly forced...
Page 48 - Before the blowpipe it decrepitates, and fuses into a dark grey mass in which globules of reduced lead are visible ; with a little borax it forms a brownish globule, and with a larger proportion forms a blue or greenish blue glass.

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