QUARTZ, is a hard vitrifiable stone, something intermediate betwixt rock-crystals and flints, or opaque vitrifiable stones. Quartz is a stone well known by metallurgists, mineralogists, and miners, as it is frequently and abundantly found with ores, of which it often forms the matrix. It is also frequently
found where no ores are.—The most common quartz is more or less of a milky-white colour, and consequently semi-transparent. Some of them have various colours. This stone, which is very hard and very compact, is nevertheless cracked throughout its substance; to which also the rock-crystal is very liable.
Quassia, but much less so than quartz. The fragments of quartz are always angular, and its internal surface has but little gloss. Quartz is a little waved, and has a greasy appearance. It is found not only of various colours, but also of various forms. It is frequently found crystallized in caverns and slits of rocks. Its crystallization is the same as that of rock-crystal. Quartz may be employed in vitrification, as all other vitrifiable stones are.