The next mineral in the scale of hardness is quartz. (Hardness 7.) When pure and colorless it should be called "_rock crystal_." Purple quartz is of course _amethyst_. Some dealers have adopted a bad practice of calling the fine deep purple amethyst "Oriental" amethyst, which should not be done, as the term "Oriental" has for a long time signified a _corundum_ gem. As Siberia has produced some very fine amethysts, the term "_Siberian amethyst_" would be a good one to designate any especially fine gem. QUARTZ GEMS. We have already considered the naming of yellow quartz in connection with topaz. "_Citrine quartz_" is probably the best name for this material. If it is felt that the name "topaz" must be used, the prefix "quartz" should be used, or perhaps "Spanish topaz" will do, but some effort should be made to distinguish it from the true precious topaz. In addition to amethyst and citrine quartz we have the pinkish, milky quartz known as "_rose quartz_." This is usually correctly named. "_Cat's-eye_" is a term that should be reserved for the Chrysoberyl variety, and the quartz variety should always be called "quartz cat's-eye." "_Tiger's-eye_" is a mineral in which a soft fibrous material has been dissolved away, and quartz has been deposited in its place. "_Aventurine quartz_" is the correct name for quartz containing spangles of mica. Clear, colorless pebbles of quartz are sometimes cut for tourists. Such pebbles are frequently misnamed "diamonds" with some prefix, as for example "Lake George diamonds," etc. Among the minutely crystalline varieties of quartz we have the clear red, which should be called "_carnelian_," the brownish-red "_sard_," the green "_chrysoprase_," the leek green "_prase_," and the brighter green "_plasma_." The last three are not so commonly seen as the first two, and frequently the best-colored specimens are artificially dyed. "_Jasper_," a material more highly regarded by the ancients than at present, is mainly quartz, but contains enough earthy material to make it opaque. "_Bloodstone_" is a greenish chalcedony with spots of red jasper. "_Agates_" are banded chalcedonies, the variety called "_onyx_" having very regular bands, and the "_sardonyx_" being an onyx agate in which some of the bands are of reddish sard.