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Gem Profile- Dumortierite

by Judy Ellis
Last week, I took my car to the shop because it was not running very well and would feel like it was misfiring when I hit about 40mph. I thought it was either the spark plugs needing to be replaced, or the engine was about to blow up... it's a Ford, it could happen. Much to my relief, the engine was fine; it just needed to have the spark plugs changed. So, what do my car woes have to do with a deep violet/blue Aluminum Borosilicate Hydroxide mineral? Well, you know the high grade ceramic tips used in spark plugs... they're made with dumortierite!
What is Dumortierite?

Dumortierite (doo-MOHR-tir-ite) has a hardness of 7-8.5, making it suitable for both industrial uses and ornamental purposes, including countertops and jewelry.

It is ideal for cabochons because of its fibrous inclusions and vitreous translucent luster.

The fibers within the stone make it very durable but also difficult to facet.

Some finer-grained specimens can be faceted and have been used to create beautiful carvings.
Dumortierite is fairly rare and often mistaken for lapis or sodalite because of its vivid blue color.

One way to tell them apart is that sodalite contains calcite, and lapis has pyrite inclusions.

Dumortierite lacks these white or metallic flecks. Its blue is a deep, fibrous denim, unlike lapis, which is brighter.

Adding to the variety, dumortierite can also appear purple, similar to lepidolite.

However, it is fibrous, has no mica flecks, and cannot be scratched with a knife.
Judy Ellis's Gem Profile- Dumortierite - , General Education, , Oval Dumortierite Beads
How Dumortierite was Discovered

Dumortierite is named after its discoverer, Eugene Dumortier, a French paleontologist from Lyon.

On November 13, 1879, Dumortier and his colleague Ferdinand Gonnard were doing fieldwork near Lyon when they found a striking blue fibrous mineral in a gneiss block. They collected a sample and brought it back to the lab.

After testing, Gonnard confirmed it was a new mineral and published a paper in 1881 naming it after Dumortier.

Since then, dumortierite deposits have been found worldwide, including in France, the United States, Canada, Madagascar, and Russia.
Judy Ellis's Gem Profile- Dumortierite - , General Education, , Faceted Dumortierite beads
Finding Dumortierite: Road Trip!

Since my car needed repairs and a plane ticket is out of the budget, we'll skip France and Russia this road trip and focus on California instead!

Dumortierite is also found in Arizona, Colorado, Nevada, and New York. For this trip, we'll stick to Southern California, where the mineral comes from the Dehasa Mine northeast of San Diego. The mine isn't open for tours, but there's plenty to enjoy in the area.

San Diego offers beautiful beaches, marinas, and great food. You can also visit the Star of India in the harbor, tour the maritime museum, and check out the zoo and aquarium.

Materials

Wire
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Dumortierite 30x40mm Oval Beads - 8 Inch Strand
A1-156
  • Lesson Quantity: 1.00 pieces
  • Purchase Quantity: 1.00 each
  • Price: $21.00
  • Gold Club Price: $15.75
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Purple Dumortierite 10mm Round 8 Inch Strand
A1-843
  • Lesson Quantity: 1.00 pieces
  • Purchase Quantity: 1.00 each
  • Price: $8.07
  • Gold Club Price: $6.05
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Dumortierite Beads
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Purple Dumortierite Beads
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Cabochons
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Tools

WireJewelry - Ultimate Wire-Pliers Jewelry Pliers with Case, Set of 5
G15-20
  • G15-20
  • Lesson Quantity: 1.00 pieces
  • Purchase Quantity: 1.00 each
  • Price: $170.72
  • Gold Club Price: $128.04
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Bench Tools
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  • Category: General Education
  • Technique(s): General Education

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