Physical
& Optical Properties of Minerals & Gemstones
Hardness
Hardness: The resistance to abrading or scratching;
measured from 1 to 10 on the Mohs Scale.
Mohs Hardness Scale
|
1. |
Can be scratched easily with a fingernail. |
Talc: 1 Sulfur: 1 ½-2 |
|
2. |
Can be scratched with a fingernail. |
Gypsum: 2 Mica: 2 - 2 ½ |
|
3. |
Can be scratched with a coin. |
Calcite: 3 |
|
4. |
Can be scratched easily with a knife; cannot scratch glass. |
Rhodochrosite: 4 Fluorite: 4 |
|
5. |
Can be scratched with a knife; can just scratch glass. |
Lapis Lazuli: 5-6 Apatite: 5 Turquoise: 5-6 Opal: 5 ½-6 ½ |
|
6. |
Can be scratched with a steel file; easily scratches window/bottle glass. |
Feldspar: 6-6 ½ Pyrite: 6 ½ Tanzanite: 6 ½-7
Zircon: 6 ½-7 ½ Peridot: 6 ½-7 Moonstone: 6-6 ½ |
|
7. |
Easily scratches metal, glass, and softer stones. |
Quartzes: 7 Tourmaline: 7-7 ½ Garnet: 7-7 ½ Beryls: 7 ½-8 |
|
8. |
Scratches Quartz and softer stones. |
Topaz: 8 Chrysoberyl: 8 ½ |
|
9. |
Scratches Topaz and softer stones. |
Ruby: 9 Sapphire: 9 |
|
10. |
Scratches Ruby and Sapphire. |
Diamond: 10 |
The Hardness
Values of Various Minerals & Gemstones
|
Mineral |
Mohs |
Mineral |
Mohs |
Mineral |
Mohs |
|
|
|
|
|
|
|
|
Actinolite |
5½-6 |
Dolomite |
3½-4 |
Proustite |
2-2½ |
|
Agate |
6½-7 |
Dumortierite |
7½-8½ |
Purpurite |
4-4½ |
|
Alexandrite |
8½ |
Emerald |
7½-8 |
Pyrite |
6-6½ |
|
Almandite |
6½-7½ |
Enstatite |
5½ |
Pyrolusite |
6-6 |
|
Amazonite |
6-6½ |
Eosphorite |
5 |
Pyrope |
6½-7½ |
|
Amber |
2-2½ |
Epidote |
6-7 |
Quartz |
7 |
|
Amblygonite |
6 |
Euclase |
7½ |
Rhodochrosite |
4 |
|
Amethyst |
7 |
Fluorite |
4 |
Rhodonite |
5½-6½ |
|
Ammonite |
4 |
Garnet |
6½-7½ |
Rose Quartz |
7 |
|
Analcite |
5-5½ |
Gaspeite |
4½-5 |
Ruby |
9 |
|
Anatase |
5½-6 |
Gaylussite |
2½-3 |
Rutile |
6-6½ |
|
Andalusite |
7½ |
Glass |
5 |
Sanidine |
6 |
|
Andesine |
6-6½ |
Gold |
2½-3 |
Sapphire |
9 |
|
Andradite |
6½-7½ |
Grossularite |
6½-7½ |
Scapolite |
5½-6 |
|
Anhydrite |
3½ |
Gypsum |
2 |
Scheelite |
4½-5 |
|
Apatite |
5 |
Hauynite |
5½-6 |
Selenite |
2 |
|
Apophyllite |
4½-5 |
Heliodor |
7½-8 |
Serpentine |
2½-5½ |
|
Aquamarine |
7½-8 |
Hematite |
5½-6½ |
Siderite |
3½-4½ |
|
Aragonite |
3½-4 |
Hemimorphite |
5 |
Silver |
2½-3 |
|
Aventurine |
7 |
Hessonite |
6½-7½ |
Simpsonite |
7-7½ |
|
Axinite |
6½-7 |
Hiddenite |
6½-7 |
Sinhalite |
6½-7 |
|
Azurite |
3½-4 |
Howlite |
3-3½ |
Smaragdite |
5½ |
|
Barite |
3-3½ |
Hypersthene |
5-6 |
Smithsonite |
5 |
|
Benitoite |
6-6½ |
Idocrase |
6½ |
Smoky Quartz |
7 |
|
Beryl |
7½-8 |
Iolite |
7-7½ |
Sodalite |
5½-6 |
|
Beryllonite |
5½-6 |
Jadeite |
6½-7 |
Spessartite |
6½-7½ |
|
Bixbite |
7½-8 |
Jasper |
6½-7 |
Sphalerite |
3½-4 |
|
Boracite |
7-7½ |
Kornerupine |
6½-7 |
Sphene |
5-5½ |
|
Brazilianite |
5½ |
Kunzite |
6½-7 |
Spinel |
8 |
|
Calcite |
3 |
Kyanite |
4-7* |
Stichtite |
1½-2½ |
|
Cancrinite |
5-6 |
Labradorite |
6-6½ |
Sugilite |
6-6½ |
|
Cassiterite |
6-7 |
Lapis Lazuli |
5-6 |
Sulfur |
1½-2½ |
|
Celestite |
3-3½ |
Lazulite |
5-6 |
Taaffeite |
8 |
|
Cerussite |
3-3½ |
Leucite |
5½-6 |
Talc |
1 |
|
Chalcedony |
6½-7 |
Magnesite |
3½-4½ |
Tantalite |
6-6½ |
|
Chalcopyrite |
3½-4 |
Magnetite |
5½-6½ |
Tanzanite |
6½-7 |
|
Charoite |
5-6 |
Malachite |
3½-4 |
Tiger's Eye |
6½-7 |
|
Chrysoberyl |
8½ |
Moldavite |
5½ |
Topaz |
8 |
|
Chrysocolla |
2-4 |
Moonstone |
6-6½ |
Tourmaline |
7-7½ |
|
Chrysoprase |
6½-7 |
Morganite |
7½-8 |
Tremolite |
5-6 |
|
Cinnabar |
2-2½ |
Natrolite |
5-5½ |
Tugtupite |
5½-6 |
|
Citrine |
7 |
Nephrite |
6-6½ |
Turquoise |
5-6 |
|
Colemanite |
4½ |
Obsidian |
5-5½ |
Ulexite |
2-2½ |
|
Copper |
2½-3 |
Onyx |
7 |
Uvarovite |
6½-7½ |
|
Coral |
3-4 |
Opal |
5½-6½ |
Variscite |
4-5 |
|
Crocoite |
2½-3 |
Orthoclase |
6-6½ |
Vivianite |
1½ -2 |
|
Cubic Zirconia |
8½ |
|
2½-4½ |
Willemite |
5½ |
|
Cuprite |
3½-4 |
Periclase |
5½-6 |
Witherite |
3-3½ |
|
Danburite |
7-7½ |
Peridot |
6½-7 |
Wolframite |
5-5½ |
|
Datolite |
5-5½ |
Petalite |
6-6½ |
Wulfenite |
3 |
|
Demantoid |
6½-7½ |
Phenakite |
7½-8 |
Zincite |
4-5 |
|
Diamond |
10 |
Phosgenite |
2-3 |
Zircon |
6½-7½ |
|
Diaspore |
6½-7 |
Pollucite |
6½-7 |
Zoisite |
6-6½ |
|
Diopside |
5-6 |
Prasiolite |
7 |
|
|
|
Dioptase |
5 |
Prehnite |
6- 6½ |
|
|
**Please
note that some minerals, such as Kyanite, have
different hardness values on different crystals faces and in different
directions. This cutting resistance is of utmost importance to gem cutters.
Density
~ Specific Gravity
Specific Gravity: This is the weight ratio of a mineral due
to the density of the atomical arrangement and the
heaviness of the elements it contains. There are specialized instruments able
to measure these values.
The Specific Gravity
Values of Various Minerals & Gemstones
|
Mineral |
SG |
Mineral |
SG |
|
|
|
|
|
|
Actinolite |
3.30-3.07 |
Kyanite |
3.53-3.70 |
|
Aegirine |
3.40-3.55 |
Labradorite |
2.65-2.75 |
|
Agate |
2.60-2.64 |
Lapis Lazuli |
2.50-3.00 |
|
Almandite |
3.93-4.30 |
Lazulite |
3.04-3.14 |
|
Amazonite |
2.56-2.58 |
Leucite |
2.45-2.50 |
|
Amber |
1.05-1.09 |
Magnetite |
5.17 |
|
Amblygonite |
3.01-3.11 |
Malachite |
3.25-4.10 |
|
Amethyst |
2.65 |
Moldavite |
2.32-2.38 |
|
Ammonite |
2.75-2.80 |
Moonstone |
2.56-2.59 |
|
Analcite |
2.22-2.29 |
Muscovite |
2.78-2.88 |
|
Andalusite |
3.05-3.20 |
Natrolite |
2.20-2.26 |
|
Andesine |
2.65-2.69 |
Nephrite |
2.90-3.03 |
|
Andradite |
3.7-4.1 |
Obsidian |
2.35-2.60 |
|
Anhydrite |
2.90-2.98 |
Opal |
1.98-2.50 |
|
Apatite |
3.16-3.23 |
Orthoclase |
2.55-2.63 |
|
Apophyllite |
2.30-2.50 |
|
2.60-2.85 |
|
Aquamarine |
2.68-2.74 |
Periclase |
3.7-3.9 |
|
Aragonite |
2.94 |
Peridot |
3.28-3.48 |
|
Aventurine |
2.64-2.69 |
Petalite |
2.40 |
|
Axinite |
3.26-3.36 |
Phenakite |
2.95-2.97 |
|
Azurite |
3.7-3.9 |
Phosgenite |
6.13 |
|
Barite |
4.43-4.46 |
Pollucite |
2.85-2.94 |
|
Benitoite |
3.64-3.68 |
Prasiolite |
2.65 |
|
Beryl |
2.66-2.87 |
Prehnite |
2.82-2.94 |
|
Beryllonite |
2.80-2.87 |
Proustite |
5.51-5.64 |
|
Brazilianite |
2.98-2.99 |
Purpurite |
3.2-3.4 |
|
Calcite |
2.69-2.71 |
Pyrite |
5.00-5.20 |
|
Cancrinite |
2.42-2.51 |
Pyrolusite |
4.5-5.0 |
|
Cassiterite |
6.7-7.1 |
Pyrope |
3.62-3.87 |
|
Celestite |
3.97-4.00 |
Quartz |
2.65 |
|
Cerussite |
6.46-6.57 |
Rhodochrosite |
3.45-3.70 |
|
Chalcedony |
2.58-2.64 |
Rhodonite |
3.40-3.74 |
|
Chalcopyrite |
4.10-4.30 |
Rose Quartz |
2.65 |
|
Charoite |
2.54-2.78 |
Ruby |
3.97-4.05 |
|
Chrysoberyl |
3.70-3.78 |
Rutile |
4.20-4.30 |
|
Chrysocolla |
2.00-2.40 |
Sanidine |
2.56-2.62 |
|
Chrysoprase |
2.58-2.64 |
Sapphire |
3.95-4.03 |
|
Cinnabar |
8.0-8.2 |
Scapolite |
2.57-2.74 |
|
Citrine |
2.65 |
Scheelite |
5.9-6.3 |
|
Colemanite |
2.40-2.42 |
Selenite ~ Gypsum |
2.31-2.32 |
|
Copper |
8.94-8.95 |
Serpentine |
2.44-2.62 |
|
Coral |
2.60-2.70 |
Siderite |
3.83-3.96 |
|
Crocoite |
5.9-6.1 |
Silver |
9.6-12.0 |
|
Cubic Zirconia |
5.5-5.9 |
Simpsonite |
5.92-6.84 |
|
Cuprite |
5.85-6.15 |
Sinhalite |
3.46-3.50 |
|
Danburite |
2.97-3.03 |
Smaragdite |
3.24-3.50 |
|
Datolite |
2.90-3.00 |
Smithsonite |
4.00-4.65 |
|
Diamond |
3.50-3.53 |
Smoky Quartz |
2.65 |
|
Diaspore |
3.30-3.39 |
Sodalite |
2.14-2.40 |
|
Diopside |
3.22-3.38 |
Spessartite |
4.12-4.18 |
|
Dioptase |
3.28-3.35 |
Sphalerite |
3.90-4.10 |
|
Dolomite |
2.80-2.95 |
Sphene |
3.52-3.54 |
|
Dumortierite |
3.26-3.41 |
Spinel |
3.54-3.63 |
|
Emerald |
2.67-2.78 |
Staurolite |
3.65-3.77 |
|
Enstatite |
3.20-3.30 |
Stichtite |
2.16-2.18 |
|
Epidote |
3.3-3.5 |
Sugilite |
2.76-2.80 |
|
Euclase |
3.10 |
Sulfur |
2.05-2.08 |
|
Fluorite |
3.00-3.25 |
Taaffeite |
3.60-3.62 |
|
Gaylussite |
1.99 |
Talc |
2.55-2.80 |
|
Gold |
15.5-19.3 |
Tantalite |
5.18-8.20 |
|
Grossularite |
3.57-3.73 |
Tanzanite |
3.35 |
|
Hauynite |
2.4-2.5 |
Tiger's Eye |
2.58-2.64 |
|
Hematite |
5.12-5.28 |
Topaz |
3.49-3.57 |
|
Hemimorphite |
3.30-3.50 |
Tourmaline |
2.82-3.32 |
|
Hiddenite |
3.15-3.21 |
Tremolite |
2.95-3.07 |
|
Hornblende |
2.9-3.4 |
Tugtupite |
2.36-2.57 |
|
Howlite |
2.45-2.58 |
Turquoise |
2.31-2.84 |
|
Hypersthene |
3.4-3.5 |
Ulexite |
1.65-1.95 |
|
Idocrase |
3.32-3.47 |
Uvarovite |
3.77 |
|
Iolite |
2.58-2.66 |
Variscite |
2.42-2.58 |
|
Ivory |
1.7-2.0 |
Willemite |
3.89-4.18 |
|
Jadeite |
3.30-3.38 |
Witherite |
4.27-4.35 |
|
Jasper |
2.58-2.91 |
Wolframite |
7.1-7.6 |
|
Jet |
1.19-1.35 |
Wulfenite |
6.50-7.00 |
|
Kornerupine |
3.27-3.45 |
Zincite |
5.66 |
|
Kunzite |
3.15-3.21 |
Zircon |
3.93-4.73 |
Cleavage and
Fracture
Cleavage: The tendency of a mineral to break along a
plane due to a direction of weakness in the crystal.
Fracture: A break with an uneven or irregular surface
crack.
Minerals and
gemstones can be split along certain flat planes which are called cleavage.
Cleavage is related to the lattice (the cohesive property of the atoms) of the
crystal. The ease with which a crystal can be cleaved is referred to as being either:
perfect, good, or imperfect. Some may not be cleaved at all and are referred to
as not having cleavage.
A crystal or
gemstone can be broken with a blow which produces irregular surfaces called
fractures. Fractures are referred to as being either: conchoidal
(shell-like), uneven, smooth, fibrous, splintery, or grainy. Both the type of
cleavage and type of fracture a mineral has is important when trying to identify
a mineral. Knowing these values is also extremely helpful to lapidaries and
stone setters.
Tenacity
Tenacity: The strength of a mineral. It is also its
resistance to breaking, crushing, bending, crumbling, tearing, or changing
shape. There are several different terms used to denote a mineral’s tenacity.
They are listed below.
Elastic: It can be bent and will resume its previous shape when let
go.
Ductile: It can be pulled and made into very thin threads.
Flexible: It can easily be bent without breaking and can be shaped.
Fragile: It will easily break into pieces.
Friable: It crumbles easily.
Malleable: It can be flattened out into thin sheets
without breaking.
Sectile: It can be cut into shavings with a blade.
Optical Properties ~ Streak
Streak: A mineral's powder color. It is most easily
observed by rubbing the mineral on a piece of white unglazed porcelain, which
is known as a
streak plate.
The Streak Colors of
Various Minerals
White, Colorless, Light Gray
Actinolite, Agate, Alabaster, Alexandrite, Almandite, Amazonite, Amber, Amblygonite, Amethyst, Anatase, Andalusite, Andradite,
Anhydrite, Apatite, Apophyllite, Aquamarine,
Aragonite, Augelite, Aventurine, Axinite,
Barite, Barytocalcite, Benitoite,
Beryllonite, Brazilianite,
Calcite, Cancrinite, Carnelian, Cassiterite,
Cerussite, Chalcedony, Charoite,
Chrysoberyl, Chrysoprase,
Citrine, Celestite, Colemanite,
Coral, Cubic Zirconia, Danburite,
Datolite, Demantoid,
Diamond, Diopside, Dolomite, Dumorteirite,
Emerald, Enstatite, Epidote,
Euclase, Fluorite, Gahnite, Gaylussite,
Glass, Grossularite, Hambergite, Hauynite,
Hemimorphite, Hessonite, Hiddenite,
Howlite, Hypersthene, Idocrase, Iolite, Ivory, Jadeite, Jasper, Kornerupine, Kunzite, Kurnakovite,
Kyanite, Labradorite, Lazulite, Leucite, Linobate, Magnesite, Meerschaum, Milarite, Mimetite, Moldavite, Monazite, Moonstone, Montebrasite,
Moss Agate, Natrolite, Nephrite, Obsidian, Opal,
Orthoclase, Parisite, Periclase,
Peridot, Peristerite,
Pearl, Petalite, Phenakite,
Phosgenite, Prasiolite,
Precious Beryl, Prehnite, Pyrope,
Quartz, Rhodochrosite, Rhodonite,
Rose Quartz, Ruby, Sanidine, Sapphire, Scapolite, Scheelite, Serpentine,
Siderite, Silver, Sinhalite, Smithsonite,
Smoky Quartz, Sodalite, Spessartite,
Sphene, Spinel, Spodumene, Staurolite, Tanzanite,
Topaz, Tourmaline, Tremolite, Turquoise, Tugtupite, Ulexite, Uvarovite, Variscite, Willemite, Witherite, Wulfenite,
Zircon, and Zoisite
Red, Pink,
Cinnabar, Crocoite,
Cuprite, Friedelite, Greenockite, Hematite, Manganotantalite,
Piemontite, Proustite, Purpurite, Pyargyrite, Pyroxmangite, and Realgar
Yellow,
Chromite, Descloizite, Durangite, Fergusonite, Gold, Hubnerite, Jet, Neptunite, Rutile, Sulfur, Sphalerite, Stibiotantalite, Thorianite,
Tiger’s Eye, Vanadinite, Wurtzite,
and Zincite
Green, Yellow-Green,
Blue-Green
Bayldonite, Chrysocolla, Dioptase, Gadolinite, Gaspeite,
Hornblende, Malachite, and Marcasite
Blue, Blue-Green, Blue-Red
Azurite, Boleite,
Ceruleite, Euxenite, Lapis Lazuli, Linarite, Shattuckite, and Vivianite
Black, Gray
Anthophyllite, Aschynite, Bixbyite, Chalcopyrite, Davidite,
Ilmenite, Ilvaite,
Magnetite, Melonite, Pyrite, Pyrolusite,
Tantalite, and Wolframite
Optical
Properties ~ Refraction
Refraction: The bending of light (or any wave
phenomenon) when it moves between media with different conductive velocities.
Refractive Index: A mathematical constant equal to the ratio
of the velocity of light in a vacuum to that in the substance; it determines
the angle at which light bends when it enters a substance obliquely. There are
methods of measuring these values also.
Double Refraction: A phenomenon which occurs when the ray of
light entering a crystal is refracted and divided into two rays instead of one.
This is most commonly seen in Calcite and Zircon.
The
Refractive Indices of Various Gemstones
|
Mineral |
RI |
Mineral |
RI |
|
|
|
|
|
|
Actinolite |
1.614-1.653 |
Jet |
1.640-1.680 |
|
Adamite |
1.708-1.760 |
Kornerupine |
1.660-1.699 |
|
Aegirine |
1.700-1.800 |
Kunzite |
1.660-1.681 |
|
Agate |
1.530-1.540 |
Kyanite |
1.710-1.734 |
|
Almandite |
1.770-1.820 |
Labradorite |
1.559-1.570 |
|
Amazonite |
1.522-1.530 |
Lapis Lazuli |
1.50 |
|
Amber |
1.539-1.545 |
Lazulite |
1.612-1.646 |
|
Amblygonite |
1.578-1.646 |
Legrandite |
1.675-1.740 |
|
Amethyst |
1.544-1.553 |
Leucite |
1.504-1.509 |
|
Ammonite |
1.52-1.68 |
Magnesite |
1.509-1.717 |
|
Analcite |
1.479-1.489 |
Malachite |
1.655-1.909 |
|
Anatase |
2.488-2.564 |
Mimetite |
2.120-2.135 |
|
Andalusite |
1.627-1.649 |
Moldavite |
1.49-1.51 |
|
Andesine |
1.543-1.551 |
Montebrasite |
1.594-1.633 |
|
Andradite |
1.88-1.94 |
Moonstone |
1.518-1.526 |
|
Anglesite |
1.878-1.895 |
Natrolite |
1.480-1.493 |
|
Anhydrite |
1.570-1.614 |
Nepheline |
1.526-1.546 |
|
Apatite |
1.628-1.649 |
Nephrite |
1.600-1.627 |
|
Apophyllite |
1.535-1.537 |
Neptunite |
1.690-1.736 |
|
Aquamarine |
1.564-1.596 |
Obsidian |
1.45-1.55 |
|
Aragonite |
1.530-1.685 |
Oligoclase |
1.542-1.549 |
|
Aventurine |
1.544-1.553 |
Opal |
1.37-1.52 |
|
Axinite |
1.656-1.704 |
Painite |
1.787-1.816 |
|
Azurite |
1.720-1.848 |
Parisite |
1.671-1.772 |
|
Barite |
1.636-1.648 |
|
1.53-1.69 |
|
Benitoite |
1.757-1.804 |
Pectolite |
1.595-1.645 |
|
Beryl |
1.562-1.602 |
Periclase |
1.74 |
|
Beryllonite |
1.552-1.561 |
Peridot |
1.650-1.703 |
|
Boracite |
1.658-1.673 |
Petalite |
1.502-1.519 |
|
Brazilianite |
1.602-1.623 |
Phenakite |
1.650-1.670 |
|
Brookite |
2.583-2.700 |
Phosgenite |
2.114-2.145 |
|
Bustamite |
1.662-1.707 |
Pollucite |
1.517-1.525 |
|
Calcite |
1.486-1.658 |
Prasiolite |
1.544-1.553 |
|
Cancrinite |
1.495-1.528 |
Prehnite |
1.611-1.669 |
|
Cassiterite |
1.997-2.098 |
Proustite |
2.881-3.084 |
|
Celestite |
1.619-1.635 |
Purpurite |
1.85-1.92 |
|
Cerussite |
1.804-2.079 |
Pyrargyrite |
2.88-3.08 |
|
Chalcedony |
1.530-1.540 |
Pyrope |
1.720-1.756 |
|
Charoite |
1.550-1.561 |
Quartz |
1.544-1.553 |
|
Chrysoberyl |
1.746-1.763 |
Rhodizite |
1.690 |
|
Chrysocolla |
1.460-1.570 |
Rhodochrosite |
1.600-1.820 |
|
Chrysoprase |
1.530-1.540 |
Rhodonite |
1.716-1.752 |
|
Cinnabar |
2.905-3.256 |
Rose Quartz |
1.544-1.553 |
|
Citrine |
1.544-1.553 |
Ruby |
1.762-1.778 |
|
Clinohumite |
1.629-1.674 |
Rutile |
2.616-2.903 |
|
Clinozoisite |
1.670-1.734 |
Sanidine |
1.518-1.530 |
|
Colemanite |
1.586-1.615 |
Sapphire |
1.762-1.778 |
|
Coral |