Snowflake Obsidian - Rock Tumbler Rough
This image shows a 3-pound bag of snowflake obsidian tumbling rough, dumped into a colander and sprayed with water to reveal its full color. Click on the image for a larger view.
Snowflake Obsidian Tumbling Rough
Size: mostly 1 to 2 inch pieces
Here are a few pieces of snowflake obsidian that we tumbled. It shapes quickly in a tumbler and produces bright black tumbled stones with gray to white snowflakes.
What Is Snowflake Obsidian?
Snowflake obsidian is a product of a volcanic eruption. It formed when molten rock cooled so quickly that the atoms in the melt did not have enough time to arrange themselves into mineral crystals. Instead, the molten material immedately solidified into an amorphous solid called a "glass". So, snowflake obsidian can be called an "igneous rock" and a "volcanic glass".
What causes the snowflakes? Immediately after the rock formed it was completely black. Over time some of the glass started to alter into crystals of cristobalite, a white to gray mineral. So the white "snowflakes" are patches of cristobalite crystals within the volcanic glass.
Does It Tumble Well?
Snowflake obsidian has a Mohs hardness of about 5 1/2 to 6. It is quite a bit softer than agate and jasper. That enables it to shape quickly in a rock tumbler. One week in a rotary tumbler in medium grit is enough time to round off all of the sharp edges and produce nicely-rounded stones. Then about four or five days in fine grit will have it ready to polish.
We always use TXP aluminum oxide polish when tumbling snowflake obsidian. It produces an excellent polish in six to seven days in rotary.
The Secret to Polishing This Stuff
In addition to being soft, snowflake obsidian is brittle. That allows it to be bruised easily in a rock tumbler. But, don't allow that to discourange you from tumbling it. All you need to do to avoid bruising is to tumble snowflake obsidian in plenty of small ceramic cylinder media (you can also use large ceramic cylinder media if it has been used a few times to reduce its size).
We tumble a mix of about 50% snowflake obsidian and 50% ceramic media. The purpose of the media is to produce a smooth tumbling action. The small media also keeps large pieces of obsidian from hammering against one another during the tumble.
Finished Snowflake Obsidian Tumbled Stones:
If you don't want to tumble this snowflake obsidian yourself, we usually have medium size (5/8" to 1") tumbled stones of this material for sale by the pound. You can find them here.
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