I have a specimen from the "Tsumeb" that has tiny (up to 5.75 mm),clear colorless (non-fluorescing) crystals labeled Calcite. Given their similar crystal symmetry, how do I know these aren't Smithsonite? Given my difficulty applying a hardness test on such small crystals (they just cleave), I applied a drop or two of HCL, both to surrounding (uncrystallized), fluorescing Calcite matrix, and directly to a crystal in question.
If Calcite effervesces vigorously in HCL, and Smithsonite less so vigorously, would the crystal face need to be tested, as opposed to a cleavage surface? Should I remove a crystal and drop it in HCL, doing the same with "matrix", and comparing the results? Do you think it matters, given the unattractive nature of the overall specimen??? I also wonder if there is a practical "Zinc" test? Thanks for indulging me...
Aside of any practical tests, the xls could also be Dolomite, as well as intermediate members of several series of simple or double rhombohedral carbonates (Zn-rich Calcite, Pb-rich Calcite, Zn-rich Dolomite and even some other more exotic beasts...)
So ID may not be easy, or at least not unambiguous, without EDS. Thanks for those points. Would I at least be able to rule out Dolomite with the response these crystals show in cold, dilute HCL? Both Smithsonite and Dolomite do not react strongly in cold HCl. Only a relatively pure Calcite will Good enough. I think I have calcite, then. Thanks for your help...
