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Gemstone hardness scale

Actually almost people misunderstand about the hardness properties of gemstones. The reason is  the word has been given a specific and limited meaning by the scientific community. This definition varies considerably from the way it is used by the general public.

Hardness

Material

Absolute Hardness

1

Talc (Mg3Si4O10(OH)2)

1

2

Gypsum (CaSO4·2H2O)

3

3

Calcite (CaCO3)

9

4

Fluorite (CaF2)

21

5

Apatite (Ca5(PO4)3(OH-,Cl-,F-))

48

6

Orthoclase (KAlSi3O8)

72

7

Quartz (SiO2)

100

8

Topaz (Al2SiO4(OH-,F-)2)

200

9

Corundum (Al2O3)

400

10

Diamond (C)

1,500

The chart below is show the hardness scale of varity gemstones in market trade.

Gemstone

Hardness

Gemstone

Hardness

Gemstone

Hardness

Diamond

10

Smoky Quartz

7

Orthoclase

6 - 6.5

Star Sapphire

9

Amethyst

7

Amazonite

6 - 6.5

Color-Change Sapphire

9

Quartz

7

Sugilite

6 - 6.5

Ruby

9

Star Lemon Quartz

7

Star Sunstone

6 - 6.5

Sapphire

9

Rose Quartz

7

Moss Opal

5.5 - 6.5

Star Ruby

8.5

Citrine

7

Rhodonite

5.5 - 6.5

Chrysoberyl Cat's Eye

8.5

Ametrine

7

Boulder Opal

5.5 - 6.5

Alexandrite

8.5

Mystic Quartz

7

Fire Opal

5.5 - 6.5

Chrysoberyl

8

Tsavorite Garnet

6.5 - 7.5

Hematite

5.5 - 6.5

Mystic Topaz

8

Sillimanite Cat's Eye

6.5 - 7.5

Opal

5.5 - 6.5

Imperial Topaz

8

Spessartite Garnet

6.5 - 7.5

Opal Doublet

5.5 - 6.5

Spinel

8

Grossularite Garnet

6.5 - 7.5

Sodalite

5.5 - 6

Topaz

8

Color-Change Garnet

6.5 - 7.5

Cat's Eye Scapolite

5.5 - 6

Azotic Topaz

8

Onyx

6.5 - 7

Hackmanite

5.5 - 6

Rutile Topaz

8

Peanut Wood

6.5 - 7

Nuumite

5.5 - 6

Beryl

7.5 - 8

Tiger's Eye

6.5 - 7

Scapolite

5.5 - 6

Goshenite

7.5 - 8

Ruby-Zoisite

6.5 - 7

Moldavite

5.5

Morganite

7.5 - 8

Jasper

6.5 - 7

Lapis Lazuli

5 - 6

Emerald

7.5 - 8

Chrysoprase

6.5 - 7

Tremolite-Hexagonite

5 - 6

Cat's Eye Aquamarine

7.5 - 8

Dendritic Agate

6.5 - 7

Star Diopside

5 - 6

Aquamarine

7.5 - 8

Fire Agate

6.5 - 7

Turquoise

5 - 6

Hambergite

7.5

Star Rose Quartz

6.5 - 7

Snowflake Obsidian

5 - 5.5

Andalusite

7.5

Agate

6.5 - 7

Sphene

5 - 5.5

Dumortierite Quartz

7 - 8.5

Color-Change Diaspore
or Zultanite

6.5 - 7

Obsidian

5 - 5.5

Paraiba Tourmaline

7 - 7.5

Cassiterite

6 - 7

Smithsonite

5

Chrome Tourmaline

7 - 7.5

Maw-Sit-Sit

6 - 7

Cat's Eye Apatite

5

Iolite

7 - 7.5

Kyanite

6 - 7

Larimar

4 - 4.5

Danburite

7 - 7.5

Prehnite

6 - 6.5

Gaspeite

4 - 4.5

Rubellite Tourmaline

7 - 7.5

Labradorite

6 - 6.5

Charoite

4 - 4.5

Demantoid Garnet

7 - 7.5

Nephrite Jade

6 - 6.5

Variscite

4 - 4.5

Cat's Eye Tourmaline

7 - 7.5

Sunstone

6 - 6.5

Rhodochrosite

4

Tourmaline

7 - 7.5

Moonstone

6 - 6.5

Ammolite

4

Strawberry Quartz

7

Jadeite

6 - 6.5

Fluorite

4

Quartz Cat's Eye

7

Andesine Labradorite

6 - 6.5

Malachite

3.5 - 4

Kunzite

7

Star Moonstone

6 - 6.5

Azurite

3.5 - 4

Aventurine

7

Rainbow Moonstone

6 - 6.5

Sphalerite

3.5 - 4

Rutile Quartz

7

Rainbow Pyrite

6 - 6.5

Amber

2 - 2.5

The hardness is the ability to resist scratching. The jewelry trade relies on a unit of measure called the Moh's hardness scale to define the fragile nature of one stone compared to another. About a century ago German gem expert, Friedrich Mohs ,in 1812 and still in used today, created a scale to illustrate this. It is called the Moh’s Scale. He chose ten minerals of varying hardness and gave them each a value. His scale looks like this.