FMF - Friends of Minerals Forum, discussion and message board

[DanovskiM]

Hello,
Please help me for identification of the mineral on the copper if it possible. My initial thought was calcite, but any help with correct identification and locality information would be appreciated. I have this one from a local exchange with a collector, who said that he is from Michigan, USA.
Thanks in advance

[Tobi]

[Kevin Schofield]

looking at your photograph in detail, the associated mineral doesn't look like calcite unless it has been very etched (which is possible given that the copper has had its patina removed). The greenish colour and general form suggests to me that it may be prehnite, which is another fairly common association with copper from Michigan.

A simple acid test (bubbles if it is calcite, none if it is prehnite), or a scratch test with a steel blade (will scratch calcite, will not scratch prehnite) will tell you.

[DanovskiM]

Many thanks for your answers. I'll be trying some weekend with acid and lame.
Regards
Martin