FMF - Friends of Minerals Forum, discussion and message board

[Byron Anderson]

Several years ago I was fortunate enough to come into the possession of a prominent mineral collector's "junk box" who is no longer with us. Some of the "junk" has lifted the quality of my overall collection to new levels, but there were also a number of specimens of either unknown identification or location. Nothing of high quality, but some fun mineral mysteries nevertheless. I'm hoping with the COVID 19 situation I can take advantage of my work slow-down and post a few of the specimens to solve some of these mysteries.

The first specimen for your consideration is a grey metallic mineral with mat luster. Red-brown streak and hardness is about 6. Based on these initial property tests and crystal habit I'm thinking hematite. I can do a SG test, but hoping someone can ID based on these intiial properties and photos. Other possibilities? Location ideas?

[John Betts]

Is it magnetic?

[Kevin Conroy]

I don't know the location, but this looks like spinel-law twinned galena crystals.

[John Betts]

[Bob Morgan]

This could be martite which is hematite as a pseudomorph of magnetite. That would account for the streak and the greater hardness than magnitite.

[Bob Morgan]

It, also, would have tabular twinning on the {111}. The closest photo to this is of Prospect Peak on mindat. The matrix might be a match too.

[Kevin Conroy]

[Mark Holtkamp]

These crystals are a combination of a (trigonal) rhombohedron and a pinacoid. Quite common for hematite I think.

[Byron Anderson]

Thank you everyone for responding. I'm such a dodo. I had checked magnetism prior to posting and forgot to add it to the properties. NOT magnetic. And hardness is closer to 7. Barely scratched by the 7 pin (hardness kit). Would it help if I added a few more detail/up close photos or a video? Looks like SG may be necessary.

As a side note I thought since I first saw this specimen it was a chalcocite. I've seen photos of flattened chalcocites from Bristol that were a little similar, but a hardness test obviously squashed that identification!