http://www.gemsandimmitations.com Mon, 26 Oct 2009 20:01:32 +0000 http://backend.userland.com/rss092 en The organic products used in jewelry are quickly affected by heat.'Pearls are completely spoiled; they turn brown and split. Amber burns with a camphor-like smell, giving off black fumes. Coral loses its color and decrepitates. One other result of heating may be mentioned here, and that is the property which a ... http://www.gemsandimmitations.com/pearls-cant-take-heat/ Some brown zircons lose their color when heated, and become a brilliant white on cooling, at the same time increasing greatly in luster and brilliance. Other pale blue zircons may have their color intensified, which may or may not remain. Rubies and some other stones will change their color, which ... http://www.gemsandimmitations.com/some-minerals-loose-color/ Numbers 1 and 2 are the most convenient to use, but any or all can be made up and kept in glass test tubes ready for use. It will be realized that all varieties of quartz, whose specific gravity is about 2.66, will float on bromoform; many similarly colored stones ... http://www.gemsandimmitations.com/identifying-the-hardness-of-minerals/ In general, crystalline solids expand on being heated, and the amount of expansion is different in different directions. The expansion in volume is equal to the sum of the linear expansion along the principal axes, thus showing that the crystal form of a stone will have some bearing on the ... http://www.gemsandimmitations.com/the-effect-of-heat-on-gem-stones/ A good method of distinguishing stones is by ascertaining their specific gravities since each variety of gem stone possesses a gravity which is very nearly constant. Reference to tables, such as the one given in the Appendix, will either immediately show what the stone is or limit its identification very considerably. ... http://www.gemsandimmitations.com/specific-gravity-of-minerals/ Dust in the air contains certain small amounts of quartz and other impurities whose hardness is about 7. For this reason, stones of about 7 and under are scratched in wear fairly quickly if worn constantly, and it should be noted that emerald, quartz, and opal are amongst these. In many ... http://www.gemsandimmitations.com/hardness-of-minerals/ Here we are referring to electrical properties in a general sense, ;md although these are of great interest, they are not important as distinguishing features of any particular stone. Of course, not all gems display this property, but a few develop electricity if friction, pressure, or heat is applied. When ... http://www.gemsandimmitations.com/electrical-properties-of-gem-stones/ Jewelers often use a small file for hardness testing. If the file cuts into the stone, a fine powder is produced, thus showing that the stone is softer than the file. The hardness of a jeweler's file, which is finely cut and of hard steel, is about 6 1/2. It ... http://www.gemsandimmitations.com/hardness-testing-of-minerals/ These are the most important of all, since on them largely depends the beauty of the various gem stones. In addition, the gemologist makes use of these characteristics to determine the nature of a given specimen, and with some practice and the use of certain instruments, a stone may be ... http://www.gemsandimmitations.com/the-optical-properties-of-gem-stones/ With the development of analytical chemistry, the blowpipe method has given way to the "wet" method once more, but this is not very suitable or useful to the gemologist as it is often restricted to minerals which are soluble in some liquid. A recent method is the noting of calorimetric ... http://www.gemsandimmitations.com/blowpipe-method/