Prehnite, the Granny Smith Apple Green Mineral for Jewelry

"What's that lovely apple green stone?" I asked of my favorite Australian outback miner. Besides having that rhythmic Aussie accent, Glenn Archer has the best rocks to come out of Western Australia.

I examined the polished lime green stones with intensity, picking out the most interesting stones of just the right size for my wire-wrapped jewelry. Some stones were flawlessly opaque while others showed white inclusions. "Prehnite," he said, introducing me to a stone I had never heard of before.

Light opaque green

Besides some prehnite having white inclusions, sometimes the inclusions are black. Prehnite's color ranges from celadon to Granny Smith apple green to lime to a yellowy color. The green is never dark and always opaque. This means the stone nevers appears crystal clear and always has a cloudy, ethereal look that does not detract from the mellow, slightly yellow pastoral shade of prehnite green.

Here comes the chemistry

Prehnite is a calcium-containing aluminosilicate. Okay, here comes the boring chemical formula: Ca₂Al(AlSi₃O₁₀)(OH)_2. This tells you that prehnite isn't rare, but occurs wherever most pretty minerals are made, in rocks most anywhere including igneous, metamorphic, or volcanic. Prehnite is particularly associated with large deposits of basalt.

Pray what?

What's in its name makes prehnite unique, however. It is pronounced as "pray-night." It was the first mineral to be named not for what people did in the dark, but for a person. That person was Dutch Colonel, Henrik von Prehn, the governor of settlements at the Cape of Good Hope in South Africa for twelve years in the late 1700s. As it turns out, von Prehn was a mineralogist too and made the first discovery of the mineral that would bear his name.

His prehnite find occurred while on duty in South Africa, and the first find of any mineral to be discovered there. It turns out also that many more prehnite deposits would be found in South Africa and the rest of the world. But, the largest deposit of high quality prehnite exists near the vast basaltic deposits in Western Australia. Glenn Archer is doing his best to dig it up there.

Prehnite jewelry

The pretty green stone makes it into jewelry predominantly as beads and cabochons. Sometimes you'll see it carved, more often displayed as an interesting rough or museum quality specimen. The stones lend themselves well to tumbling and polishing, and are appreciated for the calming effect of the ever mellow green color.

Wire-wrap jewelry artists like me like to find a prehnite rough of special appeal. Of the extensive collection of prehnite that I managed to acquire from my favorite Aussie miner is an occluded polished prehnite with a burst of white. The photo shows a pendant from a particularly pretty prehnite specimen.

Pay attention to prehnite when looking for pretty rocks. And pray to find prehnite when shopping for pretty handmade jewelry.

Source:

http://www.gemcojewelry.com

http://outbackmining.com/prehnite.htm