Organic:

Amber – It is fossilized resin. Because it starts as a sticky tree resin, it sometimes contains animal and plant material as inclusions. Amber usually is found as yellow-orange-brown, but it also occurs in a range of colors.
Pearl – It is produced within the soft tissue of a living shelled mollusk. Pearls usually are seen as white, but also come in other colors, such as pink, silver, golden, green, blue, and black.

Rock Families:

Only a few gemstones belong to the rock family.

Igneous – Granite is an igneous rock.
Sedimentary – Many gemstone minerals are found in sedimentary rock (Beryl, Opal, Quartz, Turquoise, Malachite, Azurite, Chrysoprase, and Chrysocolla).
Metamorphic – Lapis is 25-40% lazurite and several other minerals, so it is considered a rock. The color is blue, violet, or greenish blue with streaks. Marble is also a metamorphic rock. Connemara Marble is a green colored marble.
Meteorites and Tektites – Moldavite is formed from a meteorite impact.

Minerals:

Most gemstones are minerals, but only a few minerals are gems. A mineral is a naturally formed solid with a crystalline structure, such as Corundum. A gem is a cut and polished solid piece used in jewelry. Sapphire and Ruby are gemstones made out of the mineral corundum.

Mineral Beryl:
Aquamarine – It is a light to dark blue or blue-green colored gem.
Emerald – It is green colored and is the most precocious gem in the beryl group.
Morganite – A pink to violet or a salmon colored gem.

Mineral Chrysoberyl:
Alexandrite – It is a green colored gem in daylight and red in artificial incandescent light.
Cat’s-Eye – Golden-yellow, green-yellow, green, brown, or red with fine inclusions that produce a silver white line that appears to move in a cabochon cut stone.

Mineral Cordierite:
Iolite – It is usually found as a blue to violet gem, but it also can be brownish.

Mineral Corundum:
Ruby – It is a red colored gem.
Sapphire – It is usually found in blue, but it can be any color, except red.

Mineral Diamond:
Diamond – It is crystallized carbon. Only one in 10,000 diamonds found is considered fancy colored (green, red, blue, purple, or yellow). There are a number of processes used to alter the color of a diamond.

Mineral Feldspar:
Moonstone – Colorless or yellowish with a pale sheen.
Aventurine – It is also called Sunstone and is an orange to red-brown gem with a metallic type shine to it.

Minerals Jadeite and Nephrite:
Jade – Green is the most common color, but it comes in other colors and multi-colored.

Mineral Malachite
Malachite is a copper carbonate hydroxide mineral and is light to black green with light and dark bands.

Mineral Olivine
Peridot – It is a yellow-green colored gem.

Mineral Opal:
White Opal – White or light colored with color play (display of rainbow like hues).
Black Opal – Dark colored (gray, blue or green) with color play.
Boulder Opal – An opal with a dark rock base with color play.
Fire Opal – Orange to red colored gem and usually does not show a play of color.

Mineral Quartz:
Amethyst – A purple or violet colored gem. It is the most highly valued gem in the quartz group.
Ametrine – Combination of the amethyst’s purple and citrine’s yellow to orange.
Chalcedony – A waxy or dull colored stone in bluish, white, gray, green, orange, red-brown, and brown. The bloodstone is dark green with red spots.
Citrine – It is light yellow to dark yellow, and golden orange to golden brown colored gem. Natural citrines are rare and most are heat treated amethysts or smoky quartzes.
Rose Quartz – It is a pink colored gem.
Smoky Quartz – It is smoky gray or brown to black colored.
Cat’s Eye – White, gray, green, yellow, or brown colored. When there are numerous fiber-like inclusions and it is cut as a cabochon, it produce a silver white line.
Tiger’s Eye – Golden yellow and golden brown opaque stone with yellow brown streaks.

Mineral Rhodochrosite:
Rhodochrosite is a manganese carbonate mineral. Raspberry red to pink are the most common colors with light and dark colored steaks.

Mineral Silicate:
Garnet Group – It is not a single species, but is composed of multiple species and varieties. The most common color is red. Gems are also found in green, yellow-green, and orange to red-brown.
Onyx – A silicate mineral formed in bands of chalcedony in alternating colors. Sardonyx is a variant in which the colored bands are sard (shades of red) rather than black. Black onyx is perhaps the most famous variety, but is not as common as onyx with colored bands.
Chalcedony – It is a cryptocrystalline form of silica, composed of very fine intergrowths of quartz and moganite. It is found in blueish, white, gray, and orange red to brown in color.

Mineral Spinel:
Spinel – One of the few gemstones that occurs in every color of the spectrum.

Mineral Spodumene:
Hiddenite – A green-yellow to green colored gem.
Kunzite – It is a pink to purple colored gem.
Triphane – It is a yellow colored gem.

Mineral Topaz:
Topaz – Yellow to orange and light to dark blue are the most common colors. It is also found in red-brown, pink-red, violet, and light green gems.

Mineral Tourmaline:
Tourmaline – Prefaced with a color, such as Pink Tourmaline. It comes in many colors and is also multicolored, such as “watermelon” (reddish pink and green).
Rubellite – A red colored Tourmaline.
Indicolite – It is a blue colored gem.
Paraiba – A bright blue to bright green Elbaite Tourmaline.

Mineral Turquoise:
Turquoise – It is sky blue, blue-green, or apple green colored. It usually has brown, dark gray, or black veins of other minerals through it.

Mineral Zircon:
Zircon – It is usually seen as blue gems. The most natural zircons are yellow, red, or brown. Also found in colorless, orange, violet, and green.

Mineral Zoisite:
Tanzanite – It is a sapphire blue, amethyst, or violet colored gem.