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

Ruby

Background:
It wasn't till about 1800 that ruby and sapphire were recognized to be of the same mineral. Ruby & Sapphire have a lot in common. They are both of the same corundum mineral, and they both have the same physical properties. Color is the distinguishing factor. Rubies are red and sapphires could be blue, white, pink, yellow, green, orange, purple, or black (sapphires other than blue are called "fancy colors"). Rubies and sapphires are harder than all other gems except diamonds. Their superior hardness combined with the lack of cleavage makes them very durable and also valuable for industrial purposes. They have been produced synthetically so they can be used as jewel bearings in watches, tips in ball-point pins, laser windows, stylus for record players, and meters & aircraft instruments.

Chemical Formula: 
Al₂O₃ - Aluminum Oxide

Species: 
Corundum

Specific Gravity:
3.95-4.05

Hardness:
9

Refractive Index (RI):
1.76-1.78

Birthstone for:
July, and 15th & 40th wedding anniversary stone

Color(s):
 Reds to pinks

Where Mined:
Primary sources in Burma, Thailand, Cambodia, Vietnam, Madagascar, Afghanistan, Pakistan, Sri Lanka, and India.

Enhancements:
Usually heat-treated to improve color and appearance. Commonly infilled.

Care:
Normal wear is fine. Can withstand ultrasonic and steam cleaning.

Pricing:
Rubies are a precious gem and can be as expensive as a diamond. Large rubies have sold for as much as $200,000 per carat, but good rubies with inclusions in the 1ct. range are available for $3,000-$4,000 per carat. Also lower quality opaque rubies are available as low as $10 per carat (not recommended). It is noted that a premium may be charged if a high grade stone originates from Mogok or shows no evidence of heat treatment.

Notes:
Rubies mined from different places often have different colors. Burmese rubies (Mogok area of Myanmar) are usually richer in color and have some pink overtones versus the darker Thai rubies. Sri Lankan rubies can tend toward pastel pinks. All should be priced differently.

Look for:
Color. Color is the most important factor in shopping. Deep rich reds are the most prized, though light shades into pinks are fun, but should be less expensive. Rubies are usually eye clean of any inclusions, though better colors with inclusions that are barely noticeable are fine. Avoid opaque or heavily included stones.

Star rubies:
These are cabochon cut stones showing bands of reflected light crossing each other in the center creating a star. This effect is called "asterism". The half of a band that starts from the center of the stone and goes to the edge is called a "ray". Star gems generally exhibit from four to twelve rays. Star sapphire and star rubies are the best known star gems. Other gems that can display a star include beryl, garnet, quartz, and spinel. Most natural star sapphires are normally more pale than natural faceted sapphires, and their stars are not as well defined as those of lab-grown (synthetic) stones. Star rubies often have a maroon rather than red color and their stars tend to be indistinctive and imperfect. Your main concern when judging a star stone

should be:
Is it easy to see the star when you look at the stone under a single, direct light source such as a penlight or light bulb?

Special Note:
Consider "Created" rubies which are of the same chemical composition as natural ones, but are "lab grown" versus mined from the ground. These created gems are available in brilliant colors and very clean making them durable and affordable. See Chatham Created Rubies in jewelplus.com online products catalog.

Sapphire

Background:
It wasn't till about 1800 that ruby and sapphire were recognized to be of the same mineral. Ruby & Sapphire have a lot in common. They are both of the same corundum mineral, and they both have the same physical properties. Color is the distinguishing factor. Rubies are red and sapphires could be blue, white, pink, yellow, green, orange, purple, or black (sapphires other than blue are called "fancy colors"). Rubies and sapphires are harder than all other gems except diamonds. Their superior hardness combined with the lack of cleavage makes them very durable and also valuable for industrial purposes. They have been produced synthetically so they can be used as jewel bearings in watches, tips in ball-point pins, laser windows, stylus for record players, and meters & aircraft instruments.

Chemical Formula:
Al₂O₃ - Aluminum Oxide

Species:
Corundum

Specific Gravity:
3.95-4.05

Hardness:
9

Refractive Index (RI):
1.76-1.78

Birthstone for:
September, and 5th & 45th wedding anniversary stone

Color(s):
Mostly blue. Fancy sapphires include any color except blue, such as: white, pink, yellow, green, orange, purple, or black . There are even blue to purple color change sapphires.

Where Mined:
Primary sources in Madagascar, Burma, Sri Lanka, Cambodia, Australia, and the USA.

Enhancements:
Usually heat-treated to produce, intensify or lighten color and improve uniformity.

Care:
Wear away! Can withstand ultrasonic and steam cleaning.

Pricing:
Dark stones are less expensive. The price increases as they lighten toward deep royal blue. Top quality Kashmir sapphires can wholesale for over $20,000 per carat. Good blue sapphires in the 1ct. range are available for $1000-$2000 per carat retail. Pale, blackish or grayish stones cost the least. The lowest priced stones often come from Australia because they tend to be overly dark and have a low transparency.

Notes:
A great wearing everyday gem.

Look for:
Dark sapphires from Thailand can look black when set. Choose a shade that lets you see blue. Ceylon sapphires (from Sri Lanka) have some royal blue shades that are fabulous. Avoid grayish overtones and deep native cuts with heavy bottoms.

Pink Sapphires:
This is the most highly prized of all the fancy color sapphires. High quality pink sapphires can cost several thousand dollars per carat.

White Sapphire:
This sapphire is made by heat-treating light colored sapphires. White sapphires are being recognized as a much more affordable alternative to diamonds.

Other Fancy color sapphires:
Yellow, green, orange, or purple sapphires are mostly mined in East Africa, Sri Lanka, Thailand, and Montana. A high percentage of green sapphire is found in Australia. Of these four sapphire colors, orange is the most valued; green is typically the lowest priced; and yellow is usually the most readily available.

Star sapphires:
These are cabochon cut stones showing bands of reflected light crossing each other in the center creating a star. This effect is called "asterism". The half of a band that starts from the center of the stone and goes to the edge is called a "ray". Star gems generally exhibit from four to twelve rays. Star sapphire and star rubies are the best known star gems. Other gems that can display a star include beryl, garnet, quartz, and spinel. Most natural star sapphires are normally more pale than natural faceted sapphires, and their stars are not as well defined as those of lab-grown (synthetic) stones. Star rubies often have a maroon rather than red color and their stars tend to be indistinctive and imperfect. Your main concern when judging a star stone should be: is it easy to see the star when you look at the stone under a single, direct light source such as a penlight or light bulb?

Special Note:
Consider "Created" sapphires which are of the same chemical composition as natural ones, but are "lab grown" versus mined from the ground. These created gems are available in brilliant colors and very clean making them durable and affordable. See Chatham Created Rubies in jewelplus.com online products catalog.

Tanzanite

Background:
Tanzanite was discovered in the 1960's in the foothills of Africa's Mt. Kilimanjaro. Later, Henry Platt, vice president and director of Tiffany's, named the stone after its country of origin, Tanzania. Tanzanite is indeed one of the most popular gems in the market. By just looking at it you can't help but fall in love with it.From one angle it may display a rich blue color, from another it can look purple to the eye. Along with the blue/purple, there may also be flashes of red, green, yellow, orange, or brown. What's more, tanzanite can appear one color indoors and another outdoors. Also a high clarity and transparency add to its beauty.

Chemical Formula:
CaAl₃(SiO₄)₃(OH) - Calcium aluminum hydroxysilicate

Species:
Zoisite

Specific Gravity:
3.20-3.40

Hardness:
6-7

Refractive Index (RI):
1.69-1.70

Birthstone for:
24th wedding anniversary stone

Color(s):
Rich purple blues

Where Mined:
Tanzania in Africa

Enhancements:
Usually heat-treated to intensify the color and /or eliminate brown, gray, or green.

Care:
Avoid temperature changes (oven to the sink or hot tub to the pool), and ultrasonic cleaners.

Pricing:
Moderately inexpensive, but can be expensive for large and/or brilliant stones with strong blue color change. You can find high quality , deep blue tanzanite with purple overtones for less than $1,200 per carat retail. Attractive light lavender tanzanite is available for less than $500 per carat retail.

Notes:
Becoming more expensive

Look for:
Good color change. Avoid grayish blues.

Topaz

Background:
Most topaz is light brown when mined and then turns colorless after exposure to light or low heat. Otherwise it tends to be pale blue.

Chemical Formula:
Al₂(F,OH)₂SiO₄ - aluminum fluorohydroxysilicate

Species:
Topaz

Specific Gravity:
3.50-3.57

Hardness:
8

Refractive Index (RI):
1.61-1.64

Birthstone for:
November, and 23rd wedding anniversary stone

Color(s):
Brown, yellow, orange, sherry, red and pink topaz mined in Brazil and Sri Lanka. Pink topaz is found in Pakistan and Russia. Blue topaz starts out pale and is irradiated to cause color.

Where Mined:
The world's largest producer of topaz is the state of Minas Gerais in Brazil. For almost 300 years, its Ouro Preto district has supplied the world with yellow, orange, and pink topaz. Other sources includes the USA, Pakistan, Sri Lanka, Russia, Germany, Mexico, Australia, and Myanmar.

Enhancements: Blue topaz is usually irradiated to produce blue.
                         Yellow/orange is occasionally irradiated to intensify the color.
                         Pink/red is usually heated to bring out the color.
                         Green is usually irradiated to produce a greener color.

Care:
Avoid long exposure to sunlight (and tanning beds) since it will cause the color to fade.

Pricing:
Yellow, orange, and pink topaz are highly regarded. High quality golden yellow or orange topaz when intensely colored and has a reddish or pink overtones, is called "imperial topaz" and may retail from about $200 to over $2,000 per carat.
Blue topaz which is produced by irradiation and then heating, can look like a fine aquamarine, but most is a stronger blue. Ever since the market was flooded with blue topaz, its price has dropped to levels below $20 per carat. Colorless topaz which is also used to simulate diamonds, is the cheapest and most plentiful topaz.

Look for:
Blue topaz should always be clean. Other colors should be clean as well, but small inclusions are acceptable.

Tourmaline

Background:
No other gemstone offers a wider variety of colors than tourmaline. Besides being found in every color of the rainbow, tourmaline may also be multi-colored in one piece. The origin of tourmaline is uncertain. It wasn't until the early 18th century that tourmaline was recognized as a distinct gemstone.

Chemical Formula:
(NaKCa)(FeLiMgMnAl)₃(AlFeCrV)₆B₃Si₆O₂₇(O,OH,F)₄

Species:
Mineral - Albaite, dravite, chrome dravite, schorl

Specific Gravity:
3.00-3.26

Hardness:
7-7 1/2

Refractive Index (RI):
1.62-1.65

Birthstone for:
Alternate birthstone of October, and 8th wedding anniversary stone

Color(s):
Virtually every color of the rainbow and combinations of two or three colors. Bicolor and tricolor tourmalines, with bands of colors are often seen.
Where Mined: Brazil, Tanzania, Kenya, Madagascar, Mozambique, Namibia, Afghanistan, Pakistan, Sri Lanka, and California and Maine in the United States.

Enhancements:
Green, blue is commonly heated to improve color and occasionally oiled and infilled.
Pink, red, and purple are occasionally heated to improve color, commonly irradiated to intensify the color, occasionally dyed and infilled.
Many colors are heated to improve color intensity. A few are filled with a resin to smooth out surface cavities.

Care:
Avoid temperature changes, ultrasonic cleaners and steam cleaning.

Notes:
Pink tourmaline almost always contains eye visible inclusions. Paraiba tourmaline was discovered only recently in 1989 in Brazil and are the only blue tourmalines around.

Pricing:
Blue tourmaline (or paraiba tourmaline) is the rarest and most expensive. In its finest qualities, it has wholesaled for over $5,000 per carat.
Top quality green tourmaline (or chrome tourmaline) can retail for as much as $2,000 per carat. However most green tourmaline, is quite affordable, with retail prices ranging from $20 per carat for low quality stones to $400 per carat for better quality stones.
Pink or red tourmaline (also called rubellite) which is clean, with intense red can retail for over $1,000 per carat.
Orange, and yellow tourmalines may retail for about $30 to $400 per carat. Brown tourmaline tends to be less expensive. Multi-colored tourmalines which have green and pink slices of crystal and have concentric color banding are called "watermelon tourmaline" and retail for about $30 to $600 per carat.
Cat's eye tourmaline retail for about $30 to $700 per carat.

Look for:
Since tourmaline is generally an included gemstone, you would want to minimize internal imperfections and look for evenness of color.

Turquoise

Background:
Turquoise is the national gemstone of Iran, where it has decorated thrones and the attire of high officials. The best turquoise occurs in the northeast of Iran near Nishapur where it has been mined for over 3000 years. The material there is typically more stable and blue than that of other sources.

Chemical Formula:
CuAl₆(PO₄)₄(OH)₈*₅H₂0 - Hydrated copper aluminum phosphate

Species:
Turquoise

Specific Gravity:
2.60-2.85

Hardness:
5-6

Refractive Index (RI):
1.61-1.65

Birthstone for:
December, and 11th wedding anniversary stone

Color(s):
Sky blue, blue-green and apple-green.

Where Mined:
Iran, USA and China.

Enhancements:
To prevent discoloration and increase durability, turquoise could be treated with a plastic substance. To improve color, a colorant may be added. Turquoise maybe impregnated with wax to deepen the color and decrease porosity.

Care:
May be discolored by perspiration, perfume, hair spray, cosmetics, lotions, heavy liquids, soap, and ultrasonic cleaning solutions. It dissolves very slowly in HCL.

Notes:
Natural turquoise has stability problems. If it is not from Iran and it is not treated, it may turn green, white, or occasionally brown within a year after it is mined. With intense heat it can fracture, shatter, crackle or discolor.

Pricing:
The most highly valued turquoise is untreated and dense and has an even, intense sky-blue color. usually this type of gem is from Iran. The value is reduced if the color is green or pale or if inclusions or lines called "spider webbing" are present. prices can range from $1 a stone to a few hundred dollars for a top quality, untreated cabochon.

Zircon

Background:
Zircon is not the same as cubic zirconia (CZ). Zircon is a natural gemstone with exceptional brilliance. Cubic zirconia is a synthetic stone with a different chemical composition. When colorless and well-cut both stones resemble diamonds. Before CZ was introduced in the market in 1976, heat-treated, colorless zircon was widely used as a diamond imitation. Zircon comes in almost every color of the spectrum.

Chemical Formula:
CZrSiO₄ - Zirconium Silicate

Species:
Zircon

Specific Gravity:
3.90-4.80

Hardness:
6-7 1/2

Refractive Index (RI):
1.78-2.01

Birthstone for:
Alternate birthstone for December

Color(s):
Blue is the most common, but zircon is also available in green, dark red, yellow, brown, and orange.

Where Mined:
Three main sources are: Cambodia, Sri Lanka, Thailand. Also found in Myanmar, Australia, Tanzania, France, and Vietnam. Bangkok is the world's cutting and marketing center for zircon.

Enhancements:
Yellows are sometimes heated to improve color. Blues, reds and clear are always heated to remove browns and intensify the main color.

Care:
Avoid abrasives and strong exposure to sunlight (and tanning beds) as they can cause fading.

Pricing:
Blue zircon often resembles aquamarine and blue topaz, but has more fire and brilliance and retails anywhere from $20 to $500 per carat.

Look for:
Most are pastel in color, but look for bright blues.