Chalcedony to as prase. 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 to nickel-bearing chrysoprase. Heliotrope is a green variety of chalcedony, containing red inclusions of iron oxide that resemble drops of blood, giving heliotrope its alternative name of bloodstone. In a similar variety, the spots are yellow instead, known as plasma. Moss agate
Selenite (mineral) a matrix (can be gypsum) or base rock. Gypsum crystals are colorless (most often selenite), white (or pearly – most often satin spar), gray, brown, beige, orange, pink, yellow, light red, and green. Colors are caused by the presence of other mineral inclusions such as, copper ores, sulfur and sulfides, silver, iron ores, coal, calcite, dolomite, and opal. Gypsum crystals can be transparent (most often selenite), translucent (most often satin spar but also selenite and gypsum flowers), and opaque (most often the rosettes and flowers). Opacity can be caused by impurities, inclusions, druse, and crust, and can occur in all