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Ethics and Integrity

Testimonials

Hi, I just happened across your site while getting ideas for my wire wrap gemstones and sea glass.

The fact that you give away information, don’t insist personal information, has bought my business already.

To add to the joy (yes, I’m prone to hyperbole but I’m absolutely enchanted with your business model), you add stone treatment information rather than burying it somewhere.

It’s very important to me to be able to tell my customers the what’s been done to their stones, the quality, source and composition of the gems they buy.

I believe I’m the only vendor to have the FCC and AGIA disclosure booklets available at any festival I’ve attended.

You have a customer now and, if OK, I will use your page on stone treatments, with proper attribution of course, as a handout at my next festival the end of this month.

Brightest blessings,

Liz

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Stone Treatment Codes

(B) block
(D) dyed
(E) enhanced
(H) heated
(I) irradiation
(M) man made - synthetic
(N) natural
(O) oiled
(P) pressed
(S) stabilized

Hardness of Gemstones

 

MOS and Absolute Hardness of most common gemstones used in jewelry design.

The Hardness of Gemstones

 

This information is not meant as a treatise on the hardness of gemstones, but rather is provided to offer a brief introduction to the topic. Although you may not have been sitting by the computer just hoping for an article on this fascinating topic to pop up on your screen, you might find it both interesting and helpful.

 

When I began research on this topic, I wondered why jewelry designers should care about the hardness of gemstones. I didn’t have to look far to get the answer. First, hardness is used to help identify unknown gemstones. Wearing my designer hat, this got my attention. I want the vendors from whom I purchase gemstones to know what they are selling and give it the correct label. While I have purchased gemstones from vendors who obviously did not realize they were misrepresenting a stone, it is a pleasure to know that won’t happen at Magpie Gemstones. Several times, I have asked about a stone or strand that I noticed this vendor had set aside and been told that since they cannot be absolutely sure what the stone is they will not sell it.


A second reason to care about the hardness of gemstones applies mainly to those who cut them. Some stones are so soft that they should not be cut for wearable jewelry. Also, knowledge of hardness is important when grinding or polishing gemstones. Do you really want to put that relatively soft gemstone into your tumbler with steel shot? I doubt it!


Now the question follows regarding how hardness is measured in the gemstone business. The hardness of a stone can be measured by how difficult it is to scratch. In 1812, Friedrich Mohs, a German mineralogist, developed the Mohs scale which he based on ten minerals. The Mohs scale is ordinal and merely compares the hardness of one substance to that of another. Later, after the invention of the scale called a sclerometer, mineralogists were able to measure absolute hardness. The chart below includes Mohs ordinal scale as well as the absolute hardness of the ten minerals he measured. Since the invention of the sclerometer, some have reported the finding of materials harder that diamonds which may lead to future changes in this information.

 

 

Mohs Scale-Ordinal

Material

Absolute Hardness as Measured by a Sclerometer

1

Talc

1

2

Gypsum

3

3

Calcite

9

4

Fluorite

21

5

Apatite

48

6

Orthoclase

72

7

Quartz

100

8

Topaz

200

9

Corundum

400

10

Diamond

1500

 

For comparative purposes, let’s look at the chart below showing how Wikopedia references the Mohs scale to everyday objects:

 

Object

Mohs Scale Hardness

Pencil “lead”

1

Fingernail

2.2-2.5

Copper penny

3.2-3.5

Knife blade

5.5

Window glass

5.5

Steel file

6.5

 

If you have interest in a particular gemstone you may be able to locate it in the following alphabetical chart, provided by

GemSelect (http://www.gemselect.com/gem-info/gem-hardness-info.php), indicating the Mohs scale for 144 gemstones:

 

Gem

Hardness

Agate

6.5 - 7

Agate Geode

6.5 - 7

Alexandrite

8.5

Almadine Garnet

6.5 - 7.5

Amazonite

6 - 6.5

Amber

2 - 2.5

Amethyst

7

Ametrine

7

Ammolite

4

Andalusite

7.5

Andesine Labradorite

6 - 6.5

Apatite

5

Aquamarine

7.5 - 8

Aventurine

7

Axinite

6.5 - 7

Azotic Topaz

8

Azurite

3.5 - 4

Beryl

7.5 - 8

Bloodstone

6.5 - 7

Boulder Opal

5.5 - 6.5

Calcite

3

Carnelian

6.5 - 7

Cassiterite

6 - 7

Cat's Eye Apatite

5

Cat's Eye Aquamarine

7.5 - 8

Cat's Eye Diaspore

6.5 - 7

Cat's Eye Scapolite

5.5 - 6

Cat's Eye Tourmaline

7 - 7.5

Chalcedony

6.5 - 7

Charoite

4.5 - 5

Chrome Diopside

5 - 6

Chrome Tourmaline

7 - 7.5

Chrysoberyl

8.5

Chrysoberyl Cat's Eye

8.5

Chrysocolla

2 - 4

Chrysoprase

6.5 - 7

Citrine

7

Clinohumite

6

Color Change Diaspore

6.5 - 7

Color Change Garnet

6.5 - 7.5

Color Change Sapphire

9

Coral

3 - 4

Danburite

7 - 7.5

Demantoid Garnet

7 - 7.5

Dendritic Agate

6.5 - 7

Diamond

10

Dumortierite Quartz

7 - 8.5

Emerald

7.5 - 8

Fire Agate

6.5 - 7

Fire Opal

5.5 - 6.5

Fluorite

4

Fossil Coral

6.5 - 7

Gaspeite

4.5 - 5

Goshenite

7.5 - 8

Grossularite Garnet

6.5 - 7.5

Hackmanite

5.5 - 6

Hambergite

7.5

Hematite

5.5 - 6.5

Hemimorphite

5

Hessonite Garnet

6.5 - 7.5

Hiddenite

6.5 - 7

Idocrase

6.5

Imperial Topaz

8

Iolite

7 - 7.5

Jadeite

6 - 6.5

Jasper

6.5 - 7

Kunzite

7

Kyanite

6 - 7

Labradorite

6 - 6.5

Lapis Lazuli

5 - 6

Larimar

4.5 - 5

Lepidolite

2.5 - 3

Malachite

3.5 - 4

Mali Garnet

6.5 - 7.5

Maw-Sit-Sit

6 - 7

Melanite

6.5 - 7

Moldavite

5.5

Moonstone

6 - 6.5

Morganite

7.5 - 8

Moss Opal

5.5 - 6.5

Mystic Quartz

7

Mystic Topaz

8

Nephrite Jade

6 - 6.5

Nuumite

5.5 - 6

Obsidian

5 - 5.5

Onyx

6.5 - 7

Opal

5.5 - 6.5

Opal Doublet

5.5 - 6.5

Orthoclase

6 - 6.5

Paraiba Tourmaline

7 - 7.5

Peanut Wood

6.5 - 7

Pearl

2.5 - 4.5

Peridot

6.5 - 7

Prehnite

6 - 6.5

Pyrope Garnet

6.5 - 7.5

Quartz

7

Quartz Cat's Eye

7

Rainbow Moonstone

6 - 6.5

Rainbow Pyrite

6 - 6.5

Rhodochrosite

4

Rhodolite Garnet

6.5 - 7.5

Rhodonite

5.5 - 6.5

Rose Quartz

7

Rubellite Tourmaline

7 - 7.5

Ruby

9

Ruby-Zoisite

6.5 - 7

Rutile Quartz

7

Rutile Topaz

8

Sapphire

9

Scapolite

5.5 - 6

Seraphinite

2 - 4

Sillimanite Cat's Eye

6.5 - 7.5

Smithsonite

5

Smoky Quartz

7

Snowflake Obsidian

5 - 5.5

Sodalite

5.5 - 6

Spessartite Garnet

6.5 - 7.5

Sphalerite

3.5 - 4

Sphene

5 - 5.5

Spinel

8

Spodumene

6.5 - 7

Star Diopside

5 - 6

Star Garnet

6.5 - 7.5

Star Lemon Quartz

7

Star Moonstone

6 - 6.5

Star Rose Quartz

6.5 - 7

Star Ruby

9

Star Sapphire

9

Star Sunstone

6 - 6.5

Strawberry Quartz

7

Sugilite

6 - 6.5

Sunstone

6 - 6.5

Tanzanite

6.5 - 7

Tashmarine Diopside

5 - 6

Tiger's Eye

6.5 - 7

Tiger's Eye Matrix

6.5 - 7

Topaz

8

Tourmaline

7 - 7.5

Tremolite-Hexagonite

5 - 6

Tsavorite Garnet

6.5 - 7.5

Turquoise

5 - 6

Variscite

4 - 5

Verdite

3

Zircon

6.5 - 7.5

 

Now you know more than you probably wanted to know about the hardness of gemstones. I hope that your friends and customers will be impressed by your new knowledge.

Dr Karen Meador compiled this article and charts for us and for that we are eternally grateful.

Karen Meador

**Contributing authors are noted in the articles they wrote. All articles are copyright. You can reprint these articles as long as the original author is sited and a link to this website is included. The name Magpie Gemstones must be used as the hypertext.

Red Bow

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