Scientifically it's known as rugose coral (Grewingkia canadensis) Sadly for coral with such a beautiful color and fascinating growth pattern, it is extinct today. It's heyday was during the Ordovician period 488 million years ago to Permian Period that ended 251 million years ago.
The coral animals formed these horns often in an individual structure, although they sometimes clustered structures as colonies.The animal lived at the large end of the calcium carbonate cone and grew on top of dead coral animals.Look for them in the midwest states if you're rockhounding.
The outside of horn coral is interesting, but the real fun is inside! Traditionally, lapidarians slice it across the grain and polish it for display. The grey-brown material around the beautiful coral, is very soft. If you want to make a cab, plan to mount it in a bail that entirely encompasses the edge. I started it on my second wheel 220 grit and worked it gently. I found I could still make subtle changes up to 14,000 grit--it's that soft. Then I finished it off with a 50,000 grit to give it the best polish I could.
This second piece is more of a rough medallion than a cab, At this cut, there was a spray of coral that went all the way to the edge. I've never seen that before, so I thought I'd preserve it. This is the next slice after the one above.
CURIOSITY CUT THE CAB
Visit www.LapidaryWhisperer.com on May 24 and see if it worked out. Please share this blog with your lapidary-inclined friends, or friends who just like rocks.
See you next time,
Your Lapidary Whisperer
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