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Curious Rock/Mineral.

Posted by Robert Darabos  
Robert Darabos May 16, 2018 10:29PM
Curious rock/mineral I found today in Michigan.
It is actually garden rock here marketed as Western Sunrise Rock (something like that).
So potentially actually comes from the Western United States.

Does not scratch with a steel knife and no reaction to acid. Also does not appear to be translucent at all.

I was thinking either a.) Jasper b.) a random pretty metamorphic rock or c.) something else


Robert Darabos May 16, 2018 10:30PM
And some close ups.

Robert Darabos May 17, 2018 12:34AM
Just did a specific gravity test with some varying results.
Ranged from 2.05 - 2.8
Three different pieces.

Piezoelectric test looks like it sparks a little.
I MAY e hitting the anvil on the bottom. But maybe not. Hard to tell.
Reiner Mielke May 17, 2018 01:05AM
Looks like some sort of slag to me.
Gregg Little May 17, 2018 02:23AM
I looked at a number of landscape supplies and one actually called it granite ????. The aggregate might be a mixture of real and fake (slag?) material. The colourful stuff may be the slag like your piece which has odd looking cavities.
Robert Darabos May 17, 2018 03:52AM
I considered slag at first too but wasn't sure.
Is slag that hard?
Lukáš Křesina May 17, 2018 06:58AM
It looks like the rock called porcellanite. It is a clay fired on the contact with volcanic rocks or burning coal deposits.
Lukáš Křesina
Richard Gibson May 17, 2018 04:02PM
Agreed with Lukáš - porcellanite, also known as clinker. Very abundant in Wyoming where it is used as road metal as well as "garden rock."
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