FMF - Friends of Minerals Forum, discussion and message board

[Carles Curto]

I believe the crystals are too flat to be creedite.

[nitana2000]

Mr. Pete: I am very happy for all of you say... For me was very diifficult give a little minerals fragment, but with enought patience a give it... Thank you for your help, thank you very much.

[nitana2000]

I up a photo for all knows what I sent you... Best regards.

[Pete Modreski]

Juan (nitana2000) and all,
I'll remind you again of our discussion of Juan's small transparent, bladed crystals, from Mexico (guessed locality, Mapimi or perhaps more likely, Santa Eulalia), and associated with a green mineral, probably mimetite (originally assumed to be conichalcite). Juan posted another picture of a cluster of these crystals on July 12, with a pencil lead for scale.

So, I've had a chance to examine the mineral under my petrographic microscope, in calibrated immersion oils as I'd offered to do, after Juan mailed me some tiny fragments. The answer is, they are indeed hemimorphite. Their refractive index matches what is expected for hemimorphite--the indices (the mineral is biaxial) are in the approximate range 1.62-1.63; the published refractive indices for hemimorphite are (alpha) 1.614, (beta) 1.617, (gamma) 1.636. What I observed is nowhere near the indices of gypsum, which are much lower (near 1.52) or creedite (lower still, near 1.48).

Thus, the several people who wrote and suggested hemimorphite as the most likely identity, were correct! I'm happy to have helped identify your mineral, Juan.

Sincerely, Pete Modreski

[lluis]

Good afternoon, Pete/List

If the german that sold the sample to Joan Viñals, who sold it to me, is not wrong, the locality is Mapimi.
Mina Ojuela to be exact.

With best wishes

Lluís

P.D.: a pity that minerals could not talk! They could explain so many histories...(as a grenat that was labeled as zircon and as a corundum ruby...despite its morphology :-( I have in my collection. I supose that I am missbehaving, but I love those little errors )

[nitana2000]

Hello, Mr. Pete Modreski:
Thank you very much for your help... When I write you, I think: Is very difficult for Mr. Modreski say with this little mineral the name of it... Now, I am very happy because with your patience and your knowledge you say me the name. Thank you again. Thank you very much.
Best regards. Juan.