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Jewelry Guide - Gemstones

Semi Precious:

The Mohs Scale of Hardness

Named for the 19th century German mineralogist who created it -- the Mohs scale measures the hardness of minerals. Basically, the 10 point scale gauges the "scratchability" of stones and minerals. It is by no means a balanced scale -- the difference in hardness between 9 (ruby) and 10 (diamond) is greater than the difference between 1 (talc) and 9.

A high Mohs rating does not always mean that a gemstone is also tough. The emerald, for example, has a Mohs rating of 7.5-8.0, yet its crystal structure makes it more brittle and prone to cracking and chipping than members of the quartz family that have lower Mohs ratings. Precious metals -- gold, platinum, silver -- have a Mohs rating of about 4, which means that they can be scratched by many gemstones. Care should always be taken to store your jewelry separately.

How colored gemstones are judged

Jewelers, like buyers, consider the depth and radiance of colored gemstones the most important quality, and deep, rich translucent coloration is highly valued. No matter the particular gemstone shape -- round, pear, heart -- a balanced cut is key. Facets should be symmetrical and centered, and the stone should not have breaks or chips.

January Garnet July Ruby
February Amethyst August Peridot
March Aquamarine September Sapphire
April Diamond or White Topaz October Opal
May Emerald November Citrine
June Pearl or Moonstone December Blue Topaz

Flaws are hard to avoid in natural gemstones, and if there are not so many inclusions as to distract the eye, jewelers value these tiny irregularities as unique identifying markers. "Zoning" is a term that jewelers use to describe the color consistency of a stone -- the more consistent the color, the better.

Know your birthstone

In 1912, the American National Association of Jewelers agreed on the birthstone chart that we use today. If you don’t know your birthstone, or if you want to see what the birthstone of a friend or special someone is, look over the table below.

Other than your birthday, there are a lot of reasons to choose to wear different gemstones. Each has unique powers attributed to it that can help its wearer’s health, love prospects, and mental focus. Click on the name of any gemstone to learn more about its fascinating history and lore.

Your sign stone

Here is a good chart to find out which precious stone is generally associated with each astrological sign:

Aries (March 22-April 20) Diamond
Taurus (April 21 – May 21) Emerald
Gemini (May 22 - June 21) Agate
Cancer (June 22 - July 22) Pearl or Moonstone
Leo (July 23 – August 22) Ruby
Virgo (August –September 22) Sapphire
Libra (September 23 – October 23) Opal
Scorpio (October 24 – November 21) Sardonyx
Sagittarius (November 22 – December 21) Topaz
Capricorn (December 22 – January 21) Onyx
Aquarius (January 21 – February 21) Turquoise
Pisces (February 22 – March 21) Moonstone
The right gift for your anniversary

Every anniversary of your marriage is worth commemorating with an enduring token of love and affection. Try this guide to locate the traditional gemstone or precious metal for each major anniversary:

1. Gold
2. Garnet
3. Pearl
4. Blue Topaz
5. Sapphire
6. Amethyst
7. Onyx
8. Tourmaline
9. Lapis Lazuli
10. Diamond
11. Turquoise
12. Jade
13. Citrine
14. Opal
15. Ruby
20. Emerald
25. Silver
30. Pearl
35. Emerald
40. Ruby
45. Sapphire
50. Gold
60. Diamond