Hardness-Translucent Gemstones
Cochise College

Gemstone Properties
Virtual Geology Museum
Hall of Gemstones
Geology Home Page

Roger Weller, geology instructor ( wellerr@cochise.edu )

last edited: 10/24/07

The harder a gem is, the better it will be able to withstand being scratched.

The hardness of a gemstone is measured on its place on Mohs scale
     of hardness.
10 on Mohs scale is the hardest known naturally occurring substance
     and the honor goes to diamond.
Most faceted gems are in the range of 7 to 9 on Mohs scale.
Some softer minerals are also used for gems because of their intense
     colors and patterns.
Gems below 6 in hardness must be treated with care.

The hardest gems are at the top of this list.

star rubies-9
star sapphires-9

catseye chrysoberyl-8.5

tourmaline-7.5
agate-7
amethyst-7

carnelian-7

rose quartz-7

jasper-7

aventurine-7

chrysoprase-7

chalcedony-7

sard-7

bloodstone-7

onyx (quartz)-7

petrified wood-7

thulite-7 to 6.5

jadeite-7 to 6.5

nephrite jade-6.5 to 6

opal -6.5 to 5.5

rhodonite-6.5 to 5.5

hematite-6.5 to 5.5

sugilite-6.5 to 6

amazonite -6

moonstone-6

labradorite-6

sodalite-6 to 5.5

turquoise-6 to 5

lapis lazuli-6 to 5

charoite-6 to 5

thomsonite-5.5 to 5

obsidian-5.5 to 5

moldavite-5.5

serpentine-5.5 to 2
catseye apatite-5

larimar (pectolite)-5
smithsonite-5

variscite-5 to 4

pearl-4.5 to 2

rhodochrosite-4

azurite-4 to 3.5

coral-4 to 3

jet-4 to 2.5

chrysocolla-4 to 2

malachite-4 to 3.5

howlite-3.5 to 3
ammolite-3.5 to 3
onyx (calcite)-3

ivory-3 to 2

ulexite-2.5 to 2

amber-2.5 to 2

gypsum (satinspar, alabaster)-2