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Smooth surfaced, non-faceted cuts of gemstones, in any shape.
Cabochons Index
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Malachite - Mohs 3.5-4
Read about Malachite Find Malachite Jewelry
Marra Mamba
See Marra Mamba (often mispelled as mara mamba) under Tiger Eye.
Maw-Sit-Sit (Maw Sit Sit) (Mawsitsit) - Mohs 6.5-7
Read about Maw-Sit-Sit Find Maw-Sit-Sit Jewelry
Mica
Micas are an important group of minerals famous for cleaving in thin sheets. Although the sheets cleave off easily, the resulting flakes are fairly durable and create wonderful sparkles in rocks. There are more than 30 minerals in the mica group, including muscovite and lepidolite.
Mohs Hardness Scale
Developed by Friedrich Mohs, a number is used to indicate the relative hardness or softness of a mineral. It works on the principal that a hard mineral can scratch a softer mineral, but a soft mineral can not scratch a harder mineral. The relative scale accounts for differences in hardness simply by testing which mineral scratches another mineral. A soft mineral like fluorite can be scratched by all of the minerals above it on the scale. The higher up on the scale, the harder and more durable the gemstone is. The lower down on the scale, the softer the stone and the more TLC it requires.
- Talc
- Gypsum
- Calcite
- Fluorite
- Apatite
- Orthoclase Feldspar (Labradorite)
- Quartz (ex: amethyst)
- Topaz
- Corundum (ruby and sapphire)
- Diamond
To compare -
2.5 - Fingernail
3.5 - Penny
5.5 - Pocket Knife
6.5 - Steel File
Moonstone (Adularia) - Mohs 6.0
Read about Moonstone Find Moonstone Jewelry
Moss Agate
Agate having random pattern of inclusions, often creating the appearance of seaweed or moss. Moss agate comes in many colors, but is often green.
Muscovite - Mohs 2 - 2.5
Muscovite is a mica. It can be colorless, white, silver, yellow, green, brown, and even red or violet. A green variety, tinted by chromium, is called fuchsite.
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Opal - Mohs 5.5-6.5
Opal can be
precious - it has plays of color (the opal that Australia is famous for)
or
common - it does not have plays of color (fire opal, peruvian opal, etc)
Click here to read more about opal.
Precious opal, including boulder opal, comes predominately from Australia, but is also found elsewhere. Read more . . .
Ethiopian Opal
Lightning Ridge Black Opal
Spencer Opal, Idaho
Queensland, Australia, including Koroit & Yowah
Common Opal (Potch) is opal that does not have plays of color. Not all common opal is "common" though, read more . . .
Bubble Opal
Fire Opal
Geyserite
Hyalite
Macedonia Green Opal
Napa Yellow Opal
Peruvian Blue Opal
Peruvian Pink Opal
Satin Flash Opal
Opal Fluorite
1) Fluorite impregnated and coated with opal.
2) A fine-grained intergrown mixture of (common) opal and fluorite, in which the degree of purple color is probably an indicator of the fluorite content.
3) See Tiffany Stone.
Opalite
Synonym for Opal. Also see Opal, Common. Also see Tiffany Stone.
Opalized
Replaced by or converted into opal.
Opalized Fluorite
1) Fluorite impregnated and coated with opal.
2) A fine-grained intergrown mixture of (common) opal and fluorite, in which the degree of purple color is probably an indicator of the fluorite content.
3) See Tiffany Stone.
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Peacock Ore (Bornite)
Read about Peacock Ore Find Peacock Ore Jewelry
Peanut Wood - Mohs 7
Read about Peanut Wood Find Peanut Wood Jewelry
Petrified Wood
Petrified wood ("wood turned into stone") is fossilized wood. All of the organic materials have been replaced with minerals while maintaining the orginial structure of the wood, including details such as tree rings. Mohs hardness is usually ~ 7.
Various elements give the petrified wood a variety of colors. Carbon creates black; cobalt creates blues and greens; chromium creates strong greens; copper creates blues and greens; iron oxides create reds, rusts, browns, and yellows; manganese creates pinks and oranges; and manganese oxides create blacks.
Pietersite
See Pietersite under Tiger Eye.
Plume Agate
Agate having soft, fluffy looking inclusions that may resemble feathers, plants, or flowers. The inclusions come in a wide array of colors. Plume agate is usually named based on the geographic location it came from, although sometimes it is named based on the color of the plume.
Potch
See Opal, Common
Purple Opal
See Tiffany Stone
Pyrite - Mohs 6 - 6.5
Pyrite is an iron sulfide also called fool’s gold because its metallic brassy yellow color allows it to be confused with gold.
Pyroxene
Any of a group of common rock-foming silicate minerals found in many igneous and metamorphic rocks. Pyroxenes indicate a high temperature of crystallization with a lack of water. If water were present, an amphibole would have most likely have formed instead.
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Quartz
A large group of minerals composed of silicon dioxide. There are 2 major sub-groups:
Quartz Species - macrocrystalline (large, single crystals) - includes amethyst, aventurine, rock crystal, citrine, hawk’s eye, prasiolite, smoky quartz, rose quartz, and tiger’s eye.
Chalcedony Species - cryptocrystalline (finely grained microcrystals) - includes agate, petrified wood, chrysoprase, bloodstone, jasper, carnelian, onyx, sard, moss agate, dendritic agate, sagenitec agate, and plume agate.
For pictures & more information, visit the International Colored Gemstone Assoc.
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