Sunday, April 5, 2020

The Uncommon Beauty of Common Opal

Pendant of Precious Opal

Before I became a rockhound, I thought that opal was the flashy stone often found in rings and earrings.That type is called precious opal.  I love it, but as a lapidary I find it terribly expensive and that makes me nervous to work on it.

For lapidary purposes, I personally prefer common opal. It comes in an amazing range of colors (Colorless, white, yellow, red, orange, green, brown, black,  and blue) and patterns, making it a great material for my lapidary fun. I've even used it in two of my lapidary meal displays!

The Opal Fish slab shown with veggies

The first part was a hunk of white, banded common opal that looked for all the world to me like a slab of cooked halibut. That led me to create my first meal case I show at lapidary club shows and a county fair. Notice how the natural lines in the opal help give it that "fishy" look!

Green Opal Pickle Relish

The second was a chunk of green opal that made me think of hamburger pickle slices. I'd just started working on a hamburger meal at the time and I blythely put it into a saw to slice without examining it closely. This was the moment I learned about how easily common opal
can fall apart. The sound it made when it exploded in the closed saw was amazing.  Stopping the saw and opening the top, I was treated to a view of thousands of small bits of green opal everywhere in the saw, including the oil. Once it was cleaned up, I decided the bits looked a little like pickle relish. So I added a few small shards of red glass, and my repurposed opal was ready.


Australian Dendritic Opal

The range of common opal that is suitable for cabochons is almost limitless. The solid colors are beautiful, but since opal tends to take more of a lustre than a shine, opal with dendrites and other inclusions makes a cab with a story to tell.

In my shop, I like to work with this material. At between 5.5 and 6.5 on the Mohs Scale, it works fairly quickly, but is hard enough to hold up a bit and not disappear under the wheel.  Like I said above, the finishes aren't shiny, more of a luster. The dendritic  "kite" shows a shine at the center because the light was right over it there.

Here's a lovely piece of Blue Opal I'm looking forward to working on. It has a few gold-colored imperfections, but to me,they help tell the story.


Because common opal is amorphous (lacking a natural shape, not crystalline: perhaps a geletain
mineral), it is classed as a mineraloid. It also contains water that can range from 3 to 21 percent of its weight. It occurs in fissures of other rocks, giving it its shapes. That moisture level is why some dry out and crack. If you've purchased some opal at a show and it is in a container with water, it's probably best to keep it that way or it may craze, fracture, or lose its color.

Boulder Opal from Australia

I chose this boulder opal, not because of the precious flashes--it doesn't have any--but because the clarity of the opal shows how the bits of debris settled at the bottom when the opal was still a gelatin. If you can enlarge this image on your screen, you'll see what I mean.


Especially when I'm at shows, I tend to find opal specimens that are just incredible to look at, and I'd never want to cab.  This limb-cast is from the Blue Forest in Eden Valley, WY--which was a forest once, eons ago, but is desolate now.

Blue Forest Opal

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Be sure to visit my next blog post on May 5.  It's all about ROCK'N RESOURCES FOR TODAY! You'll love it!

Your Lapidary Whisperer

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