Search results
Results from the WOW.Com Content Network
However, the term prase is also used to describe green quartz and to a certain extent is a color-descriptor, rather than a rigorously defined mineral variety.) Blue-colored chalcedony is sometimes referred to as "blue chrysoprase" if the color is sufficiently rich, though it derives its color from the presence of copper and is largely unrelated ...
Prase is a leek-green variety of quartz that gets its color from inclusions of the amphibole actinolite. [55] [56] However, the term has also variously been used for a type of quartzite, a microcrystalline variety of quartz or jasper, or any leek-green quartz. [56]
Chert (/ tʃ ɜːr t /) is a hard, fine-grained sedimentary rock composed of microcrystalline or cryptocrystalline quartz, [1] the mineral form of silicon dioxide (SiO 2). [2] Chert is characteristically of biological origin, but may also occur inorganically as a chemical precipitate or a diagenetic replacement, as in petrified wood.
Jasper, an aggregate of microgranular quartz and/or cryptocrystalline chalcedony and other mineral phases, [1] [2] is an opaque, [3] impure variety of silica, usually red, yellow, brown or green in color; and rarely blue. The common red color is due to iron(III) inclusions. Jasper breaks with a smooth surface and is used for ornamentation or as ...
Cryptocrystalline is a rock texture made up of such minute crystals that its crystalline nature is only vaguely revealed even microscopically [1] in thin section by transmitted polarized light.
A piece of flint 9–10 cm (3.5–3.9 in) long, weighing 171 grams. Flint, occasionally flintstone, is a sedimentary cryptocrystalline form of the mineral quartz, [1] [2] categorized as the variety of chert that occurs in chalk or marly limestone.
Its color is normally apple-green, but varies from turquoise-like cyan to deep green. The darker varieties of chrysoprase are also referred to as prase . (However, the term prase is also used to describe chlorite -included quartz, and to a certain extent is a color-descriptor, rather than a rigorously defined mineral variety.)
This conglomerate consists of pebbles and cobbles of white vein quartz, red and green quartzite, sandstone, red and gray chert, and red shale. The grayish-purple to grayish-red conglomerate and sandstone is cemented largely by hematite and microcrystalline quartz. The cobbles that it contains range in size from 2.5 in (6.4 cm) to 6.5 in (17 cm).