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Gemstone Hardness

All gemstones have different hardness measured by Mohs’ scale.

The scale was developed by German gem expert, Friedrich Mohs in 1812. The scale measures gemstones from 1 to 10.

1 is the most easily scratched while 10 is the most scratch resistant.

Knowing a gemstone's hardness can help when making jewellery designs.

Prevent scratching of gemstones in a design by using gemstones of similar hardness next to each other.

Scale of Hardness

Resilience

Stones

0-1

Can scratch with your fingernail

Talc

1-1½

Can scratch with your fingernail

Gypsum
Sulphur

2-3

 

Amber

2-4

 

Ivory

3-4

Can scratch with a coin

Pearl
Coral

3½-4

 

Malachite

4

Can scratch with a knife

Rhodochrosite

Can scratch with a copper coin.

Calcite
Kyanite
(lengthwise to grain)

5-6

This gemstone scratches softer glass.

Fluorite
Lapis Lazuli
Turquoise

5½-6½

 

Opal

6-6½

Can scratch with a steel file

Kyanite (across wise to grain)
Moonstone

6½-7

Can scratch with dust. Most dust is silicate (which is a
7) clean all your gemstones below 7 with a dust free cloth.

Quartz
Tanzanite
Apatite
Peridot

7

Can scratch with glass and will scratch all other gemstones of lower scale

Citrine
Amethyst

7-7½

 

Tourmaline
Garnet

7½-8

 

Emerald

8

This gemstone will scratch lower value gemstones and quartz.

Topaz

 

Alexandrite

9

This gemstone will scratch previous stones

Ruby
Sapphire

10

This gemstone will scratch previous stones. Saws and drill-bits are often diamond-tipped. It will cut through most things.

Diamond