The Treasury of Science; Natural and Physical ...
This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1872 edition. Excerpt: ...mineral, consisting ut a mixture of various kinds of quartz, particularly of amethyst, calcedony, and jasper. It is extensively employed by lapidaries for making a varie"of ornamental objects, and also for mortars, which are employed for pulverising very hard substances. Opal. 32. This mineral is a particular variety of quartz, containing water in chemical combination. It does not occur crystallised, but mostly in compact vitreous masses, and is distinguished by the brilliant and changeable reflections of light exhibited by some of its varieties; whence the term opalescent is derived. Noble opal possesses this property in a very high degree, and is therefore much prized as a jewel. Semi-opal, or common opal, is less remarkable for its changes of colour. Hydrophone is a mineral, possessing the peculiar property of becoming transparent and iridescent only when moistened with water. Siliceous sinter and mountain meal are likewise varieties of quartz, containing water; the former is deposited in a variety of forms by hot springs, particularly by the Geyser of Iceland. The latter is an earthy deposit from siliceous waters, and, when examined under the microscope, is found to consist almost entirely of the shells of infusoria. Another kind is called polishing slate, and is employed by lapidaries for polishing stones. SECOND CLASS.--MINERALS CONTAINING METALS. FIRST ORDER--LIGHT METALS. 6th Gbodp--POTASSIUM. 33. The most important and indeed the greater number of minerals containing potassium likewise contains alumina as an essential constituent: we shall therefore describe them in the aluminous group. Of natural potassa salts, we have only to mention the nitrate and the sulphate of potassa. Nitrate of potassa, or nitre (KO, NO), ...
- 189 x 246 x 15mm | 513g
- 13 Sep 2013
- United States
- black & white illustrations