JIMMFinsman Posted June 9 Share Posted June 9 We find a lot of these washed up on the beach. I've always thought they were coal from the few hundred shipwrecks off the coast the last several hundred years. Anyone know what this is? Looks like an oil slick. Very hard rock. Not scaly like Mica but I guess it could be. Link to comment Share on other sites More sharing options...
ynot Posted June 9 Share Posted June 9 Coal would be my first thought. Try burning a small piece. 3 Darwin said: " Man sprang from monkeys." Will Rogers said: " Some of them didn't spring far enough." My Fossil collection - My Mineral collection My favorite thread on TFF. Link to comment Share on other sites More sharing options...
New Members MrNLovesRocks Posted June 9 New Members Share Posted June 9 If you want to identify it you might want to look up a some mineral and rock identification tests. I actually used the US highway administration's published guide to do some rock and mineral identification with some of my students (found at: https://highways.dot.gov/research/publications/infrastructure/FHWA-HI-91-025). If it is coal it should streak on a tile or similar, be able to be etched by steel, and burn or smoke under flame, from what I remember. Link to comment Share on other sites More sharing options...
JIMMFinsman Posted June 9 Author Share Posted June 9 Thanks for that. Ok--it does not mark like coal. Did not leave any mark. It is very hard and I tried to scrape with a steel nail and nothing. Burning had no effect. I think I mentioned we've found loads of coal pieces, practically every day you can find them here in the beach. This piece is not like the rest. Link to comment Share on other sites More sharing options...
JIMMFinsman Posted June 9 Author Share Posted June 9 Also...I've had this piece for over 10 years and if it were Peacock Coal, which it looks like, shouldn't the iridescence be gone by now? Once exposed to air it's supposed to disappear quickly. Link to comment Share on other sites More sharing options...
FranzBernhard Posted June 9 Share Posted June 9 6 minutes ago, JIMMFinsman said: It is very hard and I tried to scrape with a steel nail and nothing. Does it scratch glass? It could be obsidian or lydite/radiolarite? Radiolarite - Wikipedia Franz Bernhard Link to comment Share on other sites More sharing options...
JIMMFinsman Posted June 10 Author Share Posted June 10 Ok so it looks like this is most likely peacock coal. The outside has this hard irredescant crystalline layer. You can see in the pic where some of that is not covering the edges of the rock. I scraped in there with a nail and was able to scrape off basically coal dust. I did burn it with a lighter until it got very hot but it did not ignite or burn in any fashion. It held it's hear for about a minute. Link to comment Share on other sites More sharing options...
JIMMFinsman Posted June 10 Author Share Posted June 10 But it's stayed irredescant for a decade and should not have that any longer Link to comment Share on other sites More sharing options...
FranzBernhard Posted June 10 Share Posted June 10 4 hours ago, JIMMFinsman said: I did burn it with a lighter until it got very hot but it did not ignite or burn in any fashion. It held it's hear for about a minute. So this in anthracite, no experience with anthracite, but it need a really high temperature to ignite / glow, as far as I know. Franz Bernhard Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now