GEMSTONES
There are many types of gemstones in the world, all of different gem families, colors, and hardnesses. Gem hardness is rated on the Mohs scale of hardness, which assigns numbers from 1 to 10, with 10 representing the hardest. The intervals between the values are not equal. The numbers for a gemstone can vary depending on the exact make up of a particular stone. The test uses scratching for the basis of hardness. A harder mineral will scratch a softer one, but not the other way around. Hardness is not an indication of toughness or strength. Hard minerals can be brittle. Knowing the hardness of your gemstones can help you care for them.
A gemstone with a hardness of:
1-2 can be scratched by a fingernail
3 can be scratched by a copper coin
4-5 can be scratched by a knife
6-8 can scratch glass
9-10 can cut glass
ALEXANDRITE
Alexandrite is a rare variety of the mineral Chrysoberyl. In outdoor light it looks bluish green, and in indoor light it has a more purplish-red color.
Mohs Scale Rating: 8.5-9
BLACK OPAL
Black Opals are part of the Opal family, and are generally considered to be the most valuable of all the varieties which include White Opal, Boulder Opal, and Mexican Fire Opal.
Mohs Scale Rating: 5-6.5
STAR SAPPHIRE
Star Sapphires are Sapphires that are heavily included with rutile, causing a star-like reflection that is most visible when the stone is cut in a cabochon shape.
DENIM BLUE SAPPHIRE
This is a Blue Sapphire with a light clear blue color, rather than the traditional deeper and richer blue.
GOLDEN SAPPHIRE
Yellow and Golden Sapphires are another variety of the Corundum family.
MORGANITE
Morganite is part of the Beryl family, which makes it a cousin of the Emerald and Aquamarine gemstones. It has a delicate pink color and was named after J.P. Morgan, an avid gem collector.
Mohs Scale Rating: 7.5-8
PINK SAPPHIRE
Pink Sapphires are another variety of the Corundum family, also a 9 on the Mohs scale.
SPESSARTITE
Spessarite is part of the Garnet family and can be found in orange and brown colors. It has a hardness of 6.5-7.5 on the Mohs scale.
TOPAZ
Topaz is a gemstone that ranges in color from gold to pink to orange to brown. It has a hardness of 8 on the Mohs scale.
AMETHYST
Amethyst is a purple gemstone that is part of the Quartz family. Its purple color can range from cool bluish purple to deep reddish purple, the latter being considered gem quality.
Mohs Scale Rating: 7
BLUE SAPPHIRE
Part of the Corundum family, Blue Sapphires are valued based on the purity of their primary hue. A secondary hue of violet or purple can positively affect the color of the Sapphire, while a secondary hue of green is considered negative.
Mohs Scale Rating: 9
CITRINE
Citrine is a member of the Quartz family, and generally has a yellowish or orange color.
Mohs Scale Rating: 7
EMERALD
High quality Emeralds that are mostly free of inclusions can be used in rings, but most Emeralds on the market are of low quality, full of cracks and fractures which makes them more susceptible to breaking and therefore unsuitable for most jewelry.
Mohs Scale Rating: 7.5-8
MINT TOURMALINE
Mint Tourmalines are one of many varieties of the Tourmaline family. Tourmalines come out of the ground in all sorts of colors, sometimes at once in the bi-color and multi-color varieties.
Mohs Scale Rating: 7-7.5
PERIDOT
Peridot is a lime-green colored stone.
Mohs Scale Rating: 6.5-7
RUBY
Ruby is also part of the Corundum family. It can be found in a range of red hues, from purplish to orangish. Only red Corundum are considered to be Rubies. All other colors of Corundum are called Sapphire. Ruby has a hardness of 9 on the Mohs scale.
TANZANITE
Tanzanite is a purple gemstone that is mined exclusively in Tanzania. It has a hardness of 6-7 on the Mohs scale.
TSAVORITE
Tsavorite is another member of the Garnet family, and it has a transparent and usually intense green color. It has a hardness of 7-7.5 on the Mohs scale.