What is the Mohs scale of hardness?

Mohs’ hardness is a term meaning ‘scratch hardness’ which was introduced by German mineralogist Friedrich Mohs in 1812. Mohs created a system whereby minerals were tested to their hardness with a pointed object, with 1 being the softest and 10 being the hardest. Crystals and minerals with a high number on the Mohs scale will be able to scratch those with a lower number. Crystals and minerals that have the same number won’t scratch each other.

Mohs scale of hardness test kit

Mohs scale of hardness crystal test kit

Above is a sample of a crystal test kit which could include a:

  • solid piece of glass (aka a glass plate)
  • your fingernail
  • unglazed white porcelain tile (aka a streak plate)
  • unglazed black porcelain tile (aka a streak plate)
  • copper coin
  • magnet
  • steel nail or file
  • magnifying glass
  • knife

Examples of crystals and minerals on the Mohs scale of hardness

Name

Hardness

Tool to test with

Talc

1

Fingernail will scratch

Covellite

1½ – 2

 

Stichtite

1½ – 2½

 

Gypsum

2

Fingernail will scratch

Amber

2 – 2½

 

Fuchsite

2 – 3

 

Chrysocolla

2 – 4

 

Gold

2½ – 3

 

Lepidolite

2½ – 3

 

Silver

2½ – 3

 

Jet

2½ – 4

 

Pearl

2½ – 4½

 

Serpentine

2½ – 5½

 

Calcite

3

Copper coin will scratch

Celestine

3 – 3½

 

Howlite

3 – 3½

 

Coral

3 – 4

 

Aragonite

3½ – 4

 

Azurite

3½ – 4

 

Malachite

3½ – 4

 

Shattuckite

3½ – 4

 

Shungite

3½ – 4

 

Fluorite

4

Knife will easily scratch

Rhodochrosite

4

 

Variscite

4 – 5

 

Kyanite

4 – 7

 

Apophyllite

4½ – 5

 

Charoite

4½ – 5

 

Apatite

5

Knife will scratch

Scolecite

5 – 5½

 

Bronzite

5 – 6

 

Lapis Lazuli

5 – 6

 

Obsidian

5 – 6

 

Turquoise

5 – 6

 

Moldavite

 

Brookite

5½ – 6

 

Sodalite

5½ – 6

 

Hematite

5½ – 6½

 

Opal

5½ – 6½

 

Rhodonite

5½ – 6½

 

Feldspar

6

Steel file will scratch

Moonstone

6

 

Amazonite

6 – 6½

 

Labradorite

6 – 6½

 

Nephrite

6 – 6½

 

Prehnite

6 – 6½

 

Pyrite

6 – 6½

 

Rutile

6 – 6½

 

Sugilite

6 – 6½

 

Zoisite

6 – 6½

 

Epidote

6 – 7

 

Sunstone

6 – 7

 

Chalcedony

6½ – 7

 

Chrysoprase

6½ – 7

 

Jadeite

6½ – 7

 

Jasper

6½ – 7

 

Kunzite

6½ – 7

 

Peridot

6½ – 7

 

Onyx 6½ – 7

Garnet

6½ – 7½

 

Agate

7

 

Amethyst

7

 

Aventurine

7

 

Bloodstone

7

 

Carnelian

7

 

Chrysoprase

7

 

Citrine

7

 

Clear Quartz

7

 

Iolite

7

 

Mookaite

7

 

Petrified Wood

7

 

Quartz

7

Will scratch glass

Smokey Quartz

7

 

Tiger Eye

7

 

Tourmaline

7 – 7½

 

Dumortierite

7 – 8½

 

Aquamarine

7½ – 8

 

Emerald

7½ – 8

 

Topaz

8

Will scratch Quartz

Corundum

9

Will scratch Topaz

Ruby

9

 

Sapphire

9

 

Diamond

10

Will scratch Corundum

 

Facebook | Instagram | Pinterest

www.crystalsrock.com.au