Color: deep green
Mined: South America, Zambia and Afghanistan
Moh's Hardness: 7.5 - 8
Birthstone: May (modern birthstone), May (traditional birthstone)

Unlike almost every other gemstone, natural emeralds contain inclusions or small deposits of iron, which are not considered to decrease the value of the stone. In fact, experts consider the inclusions to be proof that the stones are natural and not lab created. Emeralds are one of the most beautiful and most popular gemstones on the market because of their brilliant green color.

Garnet: 'gär-n&t - A brittle and more or less transparent, usually red, silicate material that has vitreous luster, occurs mainly in crystals but also in massive form and in grains, is found commonly in gneiss and mica schist, and is used as a semiprecious stone or as an abrasive

Color: can be almost any color, though traditionally used in the deep red form
Mined: can be found throughout the world
Moh's Hardness: 7-7.5
Birthstone: January (modern birthstone), January (traditional birthstone) and January (Ayurvedic birthstone)

The family of minerals known as garnets are a prehistoric stone dating as far back as ancient Egypt, though garnets have made appearances throughout history, in the Bible (the story of Noah) and in earliest recorded Greek chronicles. The Greeks named the garnet from their word "granatum" meaning pomegranate seed because of the garnet's remarkable similarity to the sweet fruit.

Also see: Rhodolite Garnet

Opal: 'O-p&l - A mineral that is a hydrated amorphous silica, softer and less dense than quartz and typically with a definite and often marked iridescent play of colors

Color: a color within itself (opalescent)
Mined: most notably found in Australia, though opals can be found throughout the world
Moh's Hardness: 5-6
Birthstone: October (modern birthstone), April (mystical birthstone) and October (Ayurvedic birthstone)

Opals are a beautiful form of the mineral silica, which come in a wide variety of colors, from white and gray, to red or black. Their unique ability to play with color by diffracting light at various wavelengths give opals their opalescent color and beauty.

Rhodolite: 'rO-d&l-"It - A pink or purple garnet, used as a gem

Color: pink or pinkish purple
Mined: can be found throughout the world, Rhodesia, Madagascar, North Carolina and Tanzania
Moh's Hardness: 7-7.5
Birthstone: no

Because the rhodolite is a beautiful pinkish purple garnet, it is often called a raspberry rhodolite. The rhodolite stone has gained popularity in recent decades and is a relatively inexpensive stone to add to a collection.

Also see: Garnet (Red)

Ruby: 'rü - bE - A precious stone that is a red corundum

Color: red
Mined: most notable stones are mined in Burma (Myamar), but also in South East Asia, Africa and several states in the U.S.
Moh's Hardness: 9
Birthstone: July (modern birthstone), July (traditional birthstone), July (mystical birthstone), July and December (Ayurvedic birthstone)

Rubies are of the same family, corundum, as sapphires, but are red in color due to small amounts of chromium in their interior. Because of the lack of iron in Burmese rubies, which can darken and cloud their appearance, Burmese rubies are the most beautiful and most expensive, though rubies are found in many countries around the world.

Sapphire: 'sa-"fIr - A gem variety of corundum in transparent or translucent crystals of a color other than red; especially one of a transparent rich blue

Color: various colors, except for red (ruby)
Mined: Australia, Burma, Sri Lanka, Thailand
Moh's Hardness: 9
Birthstone: September (modern birthstone), September (traditional birthstone), May (mystical birthstone) and August (Ayurvedic birthstone)

Sapphires, of the same mineral family as rubies, corundum, can range in color from orange/pink to black - anything but red, which would make the stone a ruby. Most prized sapphires are deep blue in color. It was the deep blue color that caused ancient Persians to believe that the earth was a giant sapphire - the beautiful blue sky reflected their proof back to earth.

Tanzanite: 'tan-z&-"nIt - A mineral that is a deep blue variety of ziosite and is used as a gemstone

Color: blue to deep blue to purple
Mined: Merelani, Tanzania
Moh's Hardness: 6.5
Birthstone: no

The tanzanite is a modern stone, discovered only in 1967 in Tanzania, Africa, hence the name, Tanzanite. The tanzanite stone is relatively rare, as it is found and mined in only one place, the Merelani Hills of Tanzania, not far from from Mt. Kilamanjaro. It is believed that the tanzanite supply will die out in future future decades, unless another vein of it is found elsewhere in the world.