Unitedstatesofamerica1 21 Posted April 22, 2017 Share Posted April 22, 2017 Quote Link to post Share on other sites
weaver hillbille 488 Posted April 22, 2017 Share Posted April 22, 2017 CAn you scratch it with a pin? What color mark does it leave when scratched on the bottom of a porcelain toilet tank lid? Will it light on fire with a torch? COal? WHere found( for geologic info)? 1 Quote Link to post Share on other sites
Unitedstatesofamerica1 21 Posted April 22, 2017 Author Share Posted April 22, 2017 Found in Pennsylvania east coast the rock is heavy has specific gravity 3.3 can be scratched with a knife Quote Link to post Share on other sites
homefire 2,581 Posted April 22, 2017 Share Posted April 22, 2017 Vermiculite. https://en.wikipedia.org/wiki/Vermiculite 1 Quote Link to post Share on other sites
weaver hillbille 488 Posted April 23, 2017 Share Posted April 23, 2017 13 hours ago, homefire said: Vermiculite. https://en.wikipedia.org/wiki/Vermiculite It does look "platey" 1 Quote Link to post Share on other sites
Morlock 1,678 Posted April 23, 2017 Share Posted April 23, 2017 http://geology.com/minerals/streak-test.shtml 1 Quote Link to post Share on other sites
homefire 2,581 Posted April 23, 2017 Share Posted April 23, 2017 We have minor pockets of that here in the Florida Mtns just out of town. Hit a small bit of it with a Propane torch and it will do the pop corn thing. Eye Protection Required. 1 Quote Link to post Share on other sites
4meter 200 Posted April 25, 2017 Share Posted April 25, 2017 Looks like massive Biotite to me. The stated S.G. also match Biotite. Will it scratch your fingernail or a 1970s penny? If it peels off in flat sheets that are brittle and has a white streak, then mostly likely Biotite. Vermiculite will have a "pearly" luster along the cleavage plans, the plats will have a "greasy" feel, yellow or brown streak and are pliable (flexes like plastic), not brittle like Biotite. 1 Quote Link to post Share on other sites
Unitedstatesofamerica1 21 Posted December 2, 2017 Author Share Posted December 2, 2017 It streaks green Quote Link to post Share on other sites
4meter 200 Posted December 4, 2017 Share Posted December 4, 2017 Just to be sure, was the streak done on a "fresh" surface of the black colored mineral? Will the black mineral scratch a piece of copper? When you brake off a piece of the black mineral, do you get irregular, jagged edges or smooth edges with shapes that repeat? Last, if you hit a piece of the black mineral with a hammer, does it shatter into small pieces or does it flatten out like a piece of copper wire hit with a hammer? 1 Quote Link to post Share on other sites
Unitedstatesofamerica1 21 Posted December 4, 2017 Author Share Posted December 4, 2017 Yes I used a fresh surface of the black colored mineral and it streaked green multiple times, It scratched a piece of copper that I had as well, I really don't wont to break it Quote Link to post Share on other sites
d_day 341 Posted December 5, 2017 Share Posted December 5, 2017 Could be augite. 1 Quote Link to post Share on other sites
4meter 200 Posted December 5, 2017 Share Posted December 5, 2017 @ d_day: Augite would be a good candidate but the hardness of this sample is to soft at somewhere between 3.5-4.5 for Augite. I'm leaning toward some sort of copper mineral due to the softness and the green coloration on the sample. Still the S.G. is low for a metal salt mineral. @ poster: Can you give us a general area where you found the sample, I'm assuming its in eastern Pennsylvania. 1 Quote Link to post Share on other sites
4meter 200 Posted December 5, 2017 Share Posted December 5, 2017 Here is a candidate mineral: Alabandite a Manganese Sulfide, hardness of 3.5 to 4, black color, green streak, S.G. of 3.9-4.1, isometric crystal system which will give "pentagram" crystal faces. Alabandite is a member of the Galena group. What do the rest of you think? A positive test for manganese & sulfide would clinch it. 1 Quote Link to post Share on other sites
d_day 341 Posted December 5, 2017 Share Posted December 5, 2017 Yeah I missed where he mentioned it would scratch with a knife. That certainly rules out augite. 1 Quote Link to post Share on other sites
Unitedstatesofamerica1 21 Posted December 5, 2017 Author Share Posted December 5, 2017 Yes I found this in eastern Pennsylvania Raubsville Easton PA Quote Link to post Share on other sites
Unitedstatesofamerica1 21 Posted December 29, 2017 Author Share Posted December 29, 2017 On 12/5/2017 at 10:39 AM, 4meter said: Here is a candidate mineral: Alabandite a Manganese Sulfide, hardness of 3.5 to 4, black color, green streak, S.G. of 3.9-4.1, isometric crystal system which will give "pentagram" crystal faces. Alabandite is a member of the Galena group. What do the rest of you think? A positive test for manganese & sulfide would clinch it. Is there anyway to test if it is alabandite? Quote Link to post Share on other sites
4meter 200 Posted December 30, 2017 Share Posted December 30, 2017 Not without using strong acids and having training in wet chemical analysis of minerals. Best bet is to take it to an Assayest and have them assay the sample or if you have a near by, community friendly college/university, you could take it to the chemistry department and they might test it for manganese for you. Quote Link to post Share on other sites
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.