Alkali Feldspar Group— _Orthoclase_: Pale yellow, flesh red _Amazonite_: Yellow green to greenish blue _Moonstone_: Colorless; also white to yellowish, and reddish to bluish gray Garnet (hardness: 6.5-7.5 Mohs) A group of silicate minerals Specific gravity: 3.5-4.3 _Almandine_: Orangy red to purplish red _Almandine-spessartine_: Reddish orange _Andradite_: Yellowish green to orangy yellow to black _Demantoid_: Green to yellow green andradite _Topazolite_: Yellow to orangy yellow _Grossular_: Colorless; also orange, pink, yellow, and brown _Tsavorite_: Green to yellowish green _Hessonite_: Yellow orange to red _Pyrope_: Colorless; also pink to red _Chrome pyrope_: Orange red _Pyrope-Almadine_: Reddish orange to red purple _Pyrope-Spessartine_: Greenish yellow to purple _Malaia_: Yellowish to reddish orange to brown _Color-change garnet_: Blue green in daylight to purple red in incandescent light _Rhodolite_: Purplish red to red purple _Spessartine_: Yellowish orange _Uvarovite_: Emerald green Jade (hardness: 6 Mohs) _Nephrite_ Calcium magnesium silicate Specific gravity: 2.9-3.1 White, deep green, creamy brown _Jadeite_ Sodium aluminum silicate Specific gravity: 3.1-3.5 White, leafy and blue green, emerald green, lavender, dark blue green and greenish black, deep emerald-green Lapis lazuli (hardness: 5-5.5 Mohs) A rock composed mainly of the mineral lazurite with variable amounts of pyrite (brassy flecks) and white calcite Specific gravity: 2.7-2.9 [Illustration: Diamond Star of Sierra Leone.] Deep blue, azure blue, greenish blue (bluish color with flecks of white and gold) Opal (hardness: 5.5-6.5 Mohs) Hydrated silica Specific gravity: 1.98-2.25 _White opal_: Opaque, porcelain-like white material; colors resemble flashes or speckles _Black opal_: Flashes and speckles appear against black background _Water opal_: A transparent, colorless opal is the background for brilliant flashes of color _Fire opal_: Reddish or orange opal Peridot [Olivine] (hardness: 7 Mohs) Magnesium iron silicate Specific gravity: 3.22-3.45 Olive to lime green Quartz (hardness: 7 Mohs) Silicon dioxide or silica Specific gravity: 2.65 Coarsely crystalline varieties of silica— _Rock crystal_: Colorless _Amethyst_: Purple _Citrine_: Yellow to amber _Morion_: Black _Smoky quartz or cairngorm_: smoky gray to brown _Rose quartz_: Translucent pink _Green quartz or praziolite_: Green Cryptocrystalline varieties of silica— _Chalcedony and Jasper_ (_variable_) _Agate_: Bull’s eye agate, Iris or fire agate, Onyx, Sardonyx. _Bloodstone or heliotrope._ _Carnelian._ _Chrysoprase._ _Moss agate._ _Plasma._ _Prase._ _Sard._ _Jasper._ Spinel (hardness: 8 Mohs) Magnesium aluminum oxide Specific gravity: 3.58-4.06