FMF - Friends of Minerals Forum, discussion and message board

[Charly H]

I know there is a lot going on here!! I do not have a location for this specimen, I came across this one at auction but I have no idea what it is. I believe there is some quartz, feldspar/granite conglomerate and an epidote vein. I have no idea what the purple veins could be. There are also triangular shaped vitreous patterns along some faces of the rock. I do not know the geological term for this. Any help is appreciated thanks friends!

[Peter Megaw]

Charly, looks more like a piece of pegmatite with a granite xenolith and late epidote veining to me. Not quite sure I see purple exactly...looks like it might be fine-grained dispersed specularite. Try looking at it with a lens...should be tiny flakes with red internal reflections

[Bob Carnein]

The "triangular shaped vitreous" material looks like fluorite. What you're seeing may be the cleavage, which produces triangular crack patterns. Note that fluorite isn't always purple or blue; it can be any color. Try the hardness, which should be less than that of a knife blade (you should be able to scratch it with a knife blade). I'd agree that there appears to be some epidote; also some green organic material? The purple is too fuzzy for me to get a handle on it, but I agree with Peter--may be fine grained hematite.

[Charly H]

Thanks everyone!! Oops I forgot to add the hardness varies throughout but mostly about 4-5. I compared the specimen with some of my hematoidal quartz and I can see some similarities and some differences. There looks like more of the same mineral in larger, light patches. The green inclusions (?) are almost positive mineral not organic, I will add some more hopefully clearer photos. What is the term for those ‘triangular shaped’ textures on rock faces in geology please? Thank you for your help.

** my best attempt at a streak test on the purple spots was white-clear