Alexandrite	Amethyst	Aquamarine
Citrine	Emerald	Garnet
Jade	Moonstone	Onyx (Sardonyx)
Opal	Pearl	Peridot
Ruby	Sapphire	Tanzanite
Topaz	Tourmaline	Turquoise
Zircon

Jade

Background:
There is no other stone that is as resistance to breakage and chipping as jade. This inherent toughness made it a superior weapon and tool for early man. It was even more esteemed than diamonds or gold by some civilizations in Asia, central America, and the south pacific. The Spanish conquistadors are credited for giving us the term jade. When they learned that natives in Mexico were wearing jade to relieve kidney ailments, they called it "piedra de ijada" meaning, "stone of the loins". Gradually the Spanish term evolved to jade. The early Romans had also considered jade "lapis nephriticus" meaning, "stone of nephrite. Later the Latin term was reduced to "nephrite" and was used as an alternate word for jade. In 1863, the French chemist Augustine Damour realized that jade was two different minerals, so he coined the word "jadeite" for Burmese jade to distinguish it from Chinese jade "nephrite". The Chinese had been aware of the difference between the two jades since the mid 1700's.

Chemical Formula:
NaAl(Si₂O₆) - Sodium aluminum silicate - Jadeite

Species:
Jadeite

Specific Gravity:
3.30-3.36

Hardness:
6 1/2-7

Refractive Index (RI):
1.66-1.68

Birthstone for:
12th wedding anniversary stone

Special Note:
Jade actually comes in two types: Jadeite and Nephrite.
Jadeite - more expensive

Color(s):
Rich emerald green is the most desired, but green, mottled green and white, gray, pink, brown, mauve, yellow orange and lilac are also available.

Where Mined:
Myanmar, Guatemala (but not China)

Enhancements:
Jadeite is commonly impregnated with colorless wax . Green, white and purple jade are commonly bleached and bonded for durability.

Care:
Avoid ultrasonic cleaners

Notes:
Many appraisers will not analyze jade.

Look for:
Someone you trust. Since Jadeite is sold by the piece not by weight or size, it takes a very knowledgeable dealer to buy and sell correctly.
Nephrite - very inexpensive

Color(s):
Dark green to spinach green to almost black.

Where Mined:
Canada, Australia, United States, and Taiwan.

Enhancements:
Rarely dyed to alter the color.

Care:
Avoid chemicals and ultrasonic cleaners.

Notes:
Since Nephrite is very inexpensive you won't confuse it for Jadeite.

Moonstone

Background:
Good portion of the earth's crust (over half) is composed of minerals from the feldspar group (such as Moonstone, Amazonite, Oligoslase, and labradorite) and most are not gemstones. The word "feldspar" is derived from "field" and "spar", referring to any shiny rock that cleaves easily. In India, moonstone is considered to be a sacred stone, and it was once believed to be a solidified moonlight. Moonstone is noted for a floating light effect and sheen called adularescence, which has been compared to the light of the moon. This phenomena results from alternating layers of two kinds of feldspar, namely orthoclase and albite, which cause light to scatter.

Chemical Formula:
K(AlSi₃O₈)

Species:
Feldspar

Specific Gravity:
2.54-2.63

Hardness:
6-6.5

Refractive Index (RI):
1.52-1.54

Birthstone for:
Alternate birthstone for June

Color(s):
Typically white, colorless or light grayish blue. Also may be yellow, orange, brown, blue, or green.

Where Mined:
Major sources are in Sri Lanka, India, Burma, Brazil, and Madagascar.

Pricing:
The most valuable stones are blue and near transparent, sometimes $100 per carat.Translucent white stones can cost less than $5 per carat.

Onyx (Sardonyx)

Background:
Chalcedony composed of relatively straight, parallel layers of different colors. When the dark layers are brown or brownish red, it is often called Sardonyx. Black onyx is not really onyx, it is just chalcedony that has been dyed completely black.

Chemical Formula:
SiO₂

Species:
Microcrystalline quartz - Chalcedony

Specific Gravity:
2.58-2.64

Hardness:
6.5-7

Refractive Index (RI):
1.53-1.54

Birthstone for:
Bloodstone is March birthstone; Sardonyx is August birthstone; Onyx is 7th wedding anniversary

Color(s):
Most popular in black, but also found in brown, gray and white

Where Mined:
Primary sources are USA, Germany, Brazil, Mexico, India, and Africa.

Pricing:
About $1-$30 per piece retail. Black onyx with sandblasted designs retails for up to $100 per piece.

Opal

Background:
The ancient Latin name for opal was "Opalus", which was apparently derived from the Sanskrit word "Upala" meaning "precious stone". The Greek word for opal, "Opallios", means "to see a change (of color)". The first unrecorded discovery of opal in Australia is said to be in 1849. In 1872 boulder opal was first discovery and recorded in Queensland. Today the greatest proportion of the world's opal comes from Australia.

Chemical Formula:
SiO₂nH₂O - Silica and water, about 3 to 10% water in opals with a play-of-color.

Species:
Opal

Specific Gravity:
1.98-2.20

Hardness:
5 1/2-6 1/2

Refractive Index (RI):
1.44-1.47

Birthstone for:
October, and 14th wedding anniversary stone.

Color(s):
Opaque to translucent white with green, blue, yellow, orange, red crystals. Examining opals under an electron microscope at 20,000X magnification, reveals a mass of closely packed, tiny silica spheres. Opals show a play-of-color (a shifting of spectral colors) when the spheres are uniform size and arranged in regular 3-dimensional layers. The color or range of colors of the opal are determined by the size of the spheres. Light bends and splits as it passes through the spheres, causing spectral colors to appear at different angles. The brighter and more distinctive the play-of-color, the better the opal. It is noted here that not all opals show the play-of-color.

Where Mined:
Primary source and finest quality is produced in Australia. Also found in Mexico, Brazil, USA, Japan, and Honduras.

Enhancements:
Rarely oiled impregnated with colorless wax and resins.

Care:
Be CAREFUL! Avoid sudden temperature changes (such as the hot tub to the pool or the oven to the running water). No ultrasonic cleaners, steam, solvents and chemicals. Do NOT soak your opal in any type of oil as it will trap in the natural moisture that makes it colorful and dry it out. If you are putting it in a safety deposit box (safety deposit boxes are very dry), put it inside a zip lock with a moistened cotton ball.

Pricing:
Moderately inexpensive to expensive

Notes:
There are different types of opal:

Black Opal is mined from one place on earth:
Lightning Ridge in Australia. It features a black matrix and natural base under the opal that provides a dark background to showcase the colors.

Pricing:
Moderately expensive.
Boulder Opal also has a natural background made of ironstone with a white matrix to give the bright colors a dark background.

Look for:
Even coloring and no dead spots. Hold the loose opal up to a light and look at the crystal matrix. If there a fracture inside, make sure it doesn't go from one side to the other as that stone might easily break.

Pearl

Background:
Pearl is the most famed gemstone. Known for its beauty which does note need a lapidary to enhance it. These has been worn by the kings, queens and the rich people through all times till date. The oldest known pearl jewelry was found in the coffin of a Persian princess who died in 520 BC. Pearl is a pathological formation in pearl oyster. It is formed when a foreign particle enters the gap between the body and the shell of a Pearl Oyster. The irritation caused by the foreign particle makes the Oyster take out a secretion from its body to cover the particle. When the secretion dries up, it again creates irritation to the animal, so it again covers it with its secretion - this process continues for 3 to 6 years and a pearl is produced.

Chemical Formula:
Pearl contains nearly 92% calcium carbonate (CaCO₃) held together by conchiolin 6% and has 2% water.

Species:
Pearl

Specific Gravity:
2.60-2.78

Hardness:
3-4

Refractive Index (RI):
1.52-1.66

Birthstone for:
June, and 3rd wedding anniversary stone.

Color(s):
Pink, cream, gold, black, and white

Where Mined:
Primary sources are Japan, China, Tahiti, Australia, Indonesia, Philippines, USA and Burma.

Notes:
Natural pearls have a surface appearance - which is lustrous and looks precious. When viewed under magnification it contains discontinuous wavy lines. If dropped on a hard surface they bounce in a uniform manner.

Peridot

Background:
Peridot has been mined for over 3500 years. The oldest sources are in St. John's Islands. Egypt, in the red sea. Peridot in rich yellowish-green has sometimes been mistaken for emerald. Peridot is attractive, yet affordable.

Chemical Formula:
(Mg,Fe)₂SiO₄ - Magnesium iron silicate

Species:
Forsterite

Specific Gravity:
3.27-3.45

Hardness:
6 1/2-7

Refractive Index (RI):
1.64-1.69

Birthstone for:
August, and 16th wedding anniversary stone.

Color(s):
Lime to olive to chartuse greens. The greener the stone, and the better the clarity, the higher the value. If yellow or orange colors complement your skin, then peridot jewelry should look good on you. It is particularly flattering to people with blond or red hair.

Where Mined:
Primary sources are Pakistan and Arizona. Other sources include: Myanmar, Brazil, Kenya, China, Sri Lanka, and Norway.

Enhancements:
Rarely oiled with a colorless oil or wax to fill surface fractures. Rarely infilled to cover surface fractures.

Care:
Avoid sudden temperature changes, chemicals and ultrasonic cleaners. Can scratch easily.

Pricing:
Inexpensive to moderately inexpensive for larger sizes. A high quality peridot can be purchased for less than $150 per carat retail.

Notes:
Actually formed in volcanic occurrences, peridot has even been found in meteors.

Look for:
Clean stones, though eye visible inclusions if small are okay. Even color and cutting.