Jasper Jasper Jasper, an aggregate of microgranular quartz and/or chalcedony and other mineral phases, is an opaque, 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. The mineral aggregate breaks with a smooth surface and is used for ornamentation or as a gemstone. It can be highly polished and is used for items such as vases, seals, and snuff boxes. The specific gravity of jasper is typically 2.5 to 2.9. A green variety with red spots, known as heliotrope (bloodstone), is one of the traditional birthstones
Mineral alteration form the mineral pyrite. Opalization is the alteration of amorphous silica, often as organic remains of siliceous microfossils in lithified sedimentary rocks, into the mineraloid opal. Uralitization is the process of deuteric alteration of pyroxene (most commonly augite) to form amphibole (actinolite-tremolite). The alteration occurs during either late-stages of magmatic crystallization at low temperatures (< 500 °C) or during low-grade metamorphic events (sub-greenschist facies metamorphism). The reaction is paramorphic, meaning that the structure of the mineral is modified, but its original chemistry is retained. Mineral alteration Mineral alteration refers to the various natural processes that alter a mineral's chemical composition