Thursday, July 4, 2013

Anthracite Coal & Graphite

2 scans of a small slab of anthracite - 2013, DS
(click to enlarge)

I guess I feel obligated to finish my "Black Rock" series (started here & continued here). So, here's the "big reveal".

Well, it's like this: one can't write on a hard, granulated surface with obsidian... however, with anthracite coal you can. Which is how I now know that all my mysterious black rocks - despite how iridescent and pretty they may be - are, in the last analysis, anthracite coal. The ones with a more silvery sheen, however, make finer, more pencil-like lines, which sent me on a google search for graphite; apart from being pencil lead, I never did know exactly what it was.

Actually, the game was really given away when I found the anthracite slab above... which is glassy in the center, but, the surface of which is similar to a shimmery black poster board. Whatever it was, it wasn't obsidian.

(Note: It was also easy to pry apart in layers... and, though I still hadn't concluded it was coal, I still half-expected to find a fossil. In reality, one can find fossils in slabs of coal... and, two things on my "bucket-list" are: finding a meteorite, and finding a fossil!)

Anyway, I now know that anthracite coal is a mineral and the high-carbon metamorphic state of bituminous - ordinary household - coal. Interestingly, anthracite may be considered to be a transitional stage between ordinary bituminous coal and graphite, the latter often considered to be meta-anthracite and/or the last - and purist - metamorphic stage of coal.

Well, yeah, I guess I had hoped my mystery rocks were obsidian... but, anthracite and graphite are not the lowly, mere utilitarian minerals one might expect. Anthracite was a common replacement for jet in all that wonderful Victorian mourning jewelry... and it's been carved into sculptures as well. And, the same goes for graphite! The two beautiful figures above - the hand and shell (above, left) - were carved from graphite by Angelio Batle, found here, along with a number of others. And the graphite quill (above, right) is just one example of a whole series of really cool, carved graphite pencils (one can write with!) for sale here.

And, so ends the tale of the mysterious black rocks... ;-)


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