Agate

Gemological Information  

Color:

All colors are possible

Durability:

Excellent

Crystal Structure:

Microcrystalline

Hardness:

6.5 -7

Refractive Index:

1.544 - 1.553

Family:

Quartz

Similar Stones:

Chrysoprase, Jasper, Carnelian, Bloodstone, Onyx

Treatment:

Dying

 

Alexandrite

Gemological Information

Color:

Hues of red and green

Durability:

Excellent

Crystal Structure:

Orthorhombic

Hardness:

8.5

Refractive Index:

1.746-1.755

Family:

Chrysoberyl

Similar Stones:

Stones with similar color change: natural sapphire, garnet;synthetic sapphire and synthetic spinel

Treatment:

None

 

Amethyst

Gemological Information

Color:

Shades of purple/ violet

Durability:

Excellent

Crystal Structure:

Hexagonal (trigonal)

Hardness:

7

Refractive Index:

1.544-1.553

Family:

Quartz

Similar Stones:

Amethyst can be confused with scapolite, imitation alexandrite, purple sapphire and glass

Treatment:

Heating alters to citrine

 

 

Aquamarine

Gemological Information

Color:

Pale to medium blue, often with a modifying green component

Durability:

Very wearable

Crystal Structure:

Hexagonal

Hardness:

7.5-8.0

Refractive Index:

1.577-1.583

Family:

Beryl

Similar Stones:

Aquamarine can be confused with blue topaz, synthetic spinel, blue zircon, pale blue sapphires, kyanite, apatite, tourmaline and glass

Treatment:

Heat

 

Beryl

Gemological Information

Color:

All colors

Durability:

Durable(ex. emerald)

Crystal Structure:

Hexagonal

Hardness:

7.5-8.0

Refractive Index:

1.577-1.583

Family:

Beryl

Similar Stones:

Beryl can be confused with quartz, glass and a number of other materials depending on the color of the specimen.

Treatment:

None

 

Chrysoberyl

Gemological Information

Color:

Many colors, shades of green and brown

Durability:

Excellent

Crystal Structure:

Orthorhombic,

Hardness:

8.5

Refractive Index:

1.746-1.755

Family:

Chrysoberyl

Similar Stones:

Chrysoberyl cat's eyes can be confused with varieties of chatoyant quartz and fine tourmaline. The name Cat's-eye applies only to chatoyant chrysoberyl. In recent years, a good glass imitation of cat's eye has been developed, called Cathaystone.

Treatment:

None

 

Citrine

Gemological Information

Color:

Yellow to orange(modifying brown)

Durability:

Extremely durable

Crystal Structure:

Hexagonal

Hardness:

7.0

Refractive Index:

1.544-1.553

Family:

Quartz

Similar Stones:

Citrine can be confused with topaz, glass, yellow sapphire, heliodor, garnet varieties (such as hessonite, spessartite and grossular) and amber.

Treatment:

Heat

 

Coral

Gemological Information

Color:

Red, orange, pink, peach, black, brown, gold

Durability:

soft and fragile

Crystal Structure:

organic

Hardness:

3.5-4.0

Refractive Index:

1.486-1.658

   

Similar Stones:

Coral can be confused with plastics, ceramics, and glass

Treatment:

Dying

 

Diamond

Gemological Information

Color:

All colors

Durability:

Excellent

Crystal Structure:

Cubic

Hardness:

10.0

Refractive Index:

2.417-2.420

Family:

Stands alone

Similar Stones:

Diamonds can be confused with zircons, cubic zirconia, moissanite, YAGS, strontium titanate. leaded glass, rhinestones and synthetic rutile

Treatment:

Heating, radiation, fracture filling

Emerald

Gemological Information

Color:

Green with modifying tones of blue or yellow

Durability:

durable/can be fragile

Crystal Structure:

Hexagonal

Hardness:

7.5-8.0

Refractive Index:

1.746-1.755

Family:

Beryl

Similar Stones:

Emeralds can be confused with tourmaline, diopside, fluorite and green glass

Treatment:

Dying, fracture filling, oiling

Garnet

Gemological Information

Color:

All colors

Durability:

Extremely durable

Crystal Structure:

Cubic

Hardness:

6.5-7.0

Refractive Index:

1.73-1.76 (+ or -)

Family:

Garnet

Similar Stones:

Garnet can be confused with glass, spinel, rubies and varieties of tourmaline

Treatment:

None

Jadeite

Gemological Information

Color:

All colors

Durability:

Extremely durable

Crystal Structure:

Monoclinic

Hardness:

6.5-7.0

Refractive Index:

1.660-1.680

Family:

Jadeite

Similar Stones:

Jadeite can be confused with dyed quartz and calcite, chrysoprase, aventurine and other quartz varieties and glass.

Treatment:

Dying

 

Moonstone

Gemological Information

Color:

Colorless, white, cream, peach, brown

Durability:

Good

Crystal Structure:

Monoclinic

Hardness:

6.0-6.5

Refractive Index:

1.518-1.526

Family:

Feldspar

Similar Stones:

Moonstones can be confused with adularescent glass, synthetic spinel that has been schillerized by heating, and white chalcedony.

Treatment:

None

Nephrite

Gemological Information

Color:

Grayed green, yellow, white and black

Durability:

Excellent

Crystal Structure:

Monoclinic

Hardness:

6.6

Refractive Index:

1.60-1.63

Family:

Jade

Similar Stones:

Nephrite is often confused with serpentine, green grossular garnet, soapstone, green jasper and aventurine

Treatment:

None

Onyx

Gemological Information

Color:

Banded usually black and white

Durability:

Good

Crystal Structure:

Microcrystalline

Hardness:

7.0

Refractive Index:

1.564-1.660

Family:

Microcystalline Quartz

Similar Stones:

molded plastics, glass and porcelain make excellent imitations for cameo carvings.

Treatment:

Dying

Opal

Gemological Information

 

Color:

Colorless, white, black, orange, yellow

Durability:

Relatively poor

Crystal Structure:

Amorphous

Hardness:

5.5-6.0

Refractive Index:

1.43-1.47

Family:

Mineraloid

Similar Stones:

Glass (slocum stone)and plastics are occasionally used to imitate opal, but do so poorly. The only natural substance that resembles opal is labradorite feldspar. 
Mexican fire opal may appear similar to topaz, citrine, spessartite garnet, chrysoberyl, and carnelian

Treatment:

Fracture filling

Pearl

Gemological Information

 

Color:

All colors

Durability:

Moderate

Crystal Structure:

Organic

Hardness:

2.4-4.0

Refractive Index:

1.530-1.685

Family:

 

Similar Stones:

 

Treatment:

Dying, bleaching

 

Peridot

Gemological Information

 

Color:

Medium green with yellow or brown modifiers

Durability:

Sensitive to heat

Crystal Structure:

Orthrothrombic

Hardness:

6.5-7.0

Refractive Index:

1.654-1.690

Family:

 

Similar Stones:

Peridot can be confused with emerald, apatite, demantoid or tsavorite garnets, tourmaline, chrysoberyl, sinhalite , moldavites and green zircon

Treatment:

None

 

Quartz

Gemological Information

 

Color:

All colors

Durability:

excellent

Crystal Structure:

Hexagonal

Hardness:

7.0

Refractive Index:

1.544-1.553

Family:

Quartz

Similar Stones:

 

Treatment:

Varies, depending on the variety

Ruby

Gemological Information

 

Color:

Red

Durability:

Excellent

Crystal Structure:

hexagonal

Hardness:

9

Refractive Index:

1.762-1.770

Family:

 

Similar Stones:

Ruby can be confused with garnet, spinel, red tourmaline and red beryl

Treatment:

Heat, fracture filling, bulk diffusion with beryllium

Sapphire

Gemological Information

 

Color:

Every color except red

Durability:

Excellent

Crystal Structure:

Hexagonal

Hardness:

9

Refractive Index:

1.762-1.770

Family:

 

Similar Stones:

 

Treatment:

Heat, fracture filling; bulk diffusion with beryllium

Spinel

Gemological Information

 

Color:

All colors

Durability:

excellent

Crystal Structure:

Cubic

Hardness:

8

Refractive Index:

1.714-1.75

Family:

Spinel is a group of minerals

Similar Stones:

Spinels can be confused with ruby, sapphire, pyrope garnet, amethyst and zircon. 
Synthetic spinel is inexpensively manufactured in large quantities and is used to imitate ruby, sapphire, emerald, aquamarine, peridot, alexandrite and diamond.

Treatment:

None

Tanzanite

Gemological Information

 

Color:

Blue with violet modifiers

Durability:

cleaves easily

Crystal Structure:

orthrohombic

Hardness:

6.0-7.0

Refractive Index:

1.746-1.755

Family:

Zoisite

Similar Stones:

Tanzanite can be confused with sapphire, spinel, amethyst and a synthetic variety of the mineral forsterite.

Treatment:

Heat

Topaz

Gemological Information

 

Color:

Colorless, pale green, blue, pink, salmon, champagne, peach and the very rare re

Durability:

Good

Crystal Structure:

Orthorhombic

Hardness:

8.0

Refractive Index:

1.619-1.627

Family:

 

Similar Stones:

Topaz can be confused with citrine, tourmaline, sapphire, chrysoberyl, danburite, andalusite and apatite. Unethical trade names include Madiera topaz and Smokey topaz which are used to describe quartz varietites.

Treatment:

Blue varieties are usually the result of irradiation and heat treatment. Mystic topaz is coated

Tourmaline

Gemological Information

 

Color:

All colors

Durability:

Excellent

Crystal Structure:

Trigonal

Hardness:

7.0-7

Refractive Index:

1.624-1.644

Family:

Tourmaline

Similar Stones:

Tourmaline can be confused with topaz, emerald, aquamarine, morganite, golden beryl, kunzite, hiddenite, peridot, andalusite and apatite. Dark green synthetic spinel is sold as imitation tourmaline.

Treatment:

Heat

Turquoise

Gemological Information

 

Color:

Turquoise, blues, greens

Durability:

Fair to poor

Crystal Structure:

Triclinic; rarely forms crystals

Hardness:

5.0-6.0

Refractive Index:

1.62 Average

Family:

 

Similar Stones:

Turquoise can be confused with chrysocolla, odontolie (a natually stained fossilized bone, varisite and malachite. Imitation turquise includes glass, porcelain, plastic, enamel, stained chalcedony and dyed howlite.

Treatment:

Dying, sealing

Zircon

Gemological Information

 

Color:

Colorless, orange,yellow, brown, red, blue,violet and green have been observed

Durability:

Good

Crystal Structure:

Tetragonal

Hardness:

7.50

Refractive Index:

High Zircon:1.9-2.0

Family:

Zircon

Similar Stones:

Zircons can be confused with diamonds and accasionally varieties of chrysoberyl or tourmaline. Zircons can also be confused with diamond imitations such as cubic zirconia, moisanite, YAG, GGG and strontium titanate.

Treatment:

Heat