Scanning electron microscope analysis has revealed that one of the specimens in our Phosphates case isn’t exactly what we thought it was at first.
Mimetite from Zambia is actually Pyromorphite from Zambia.
Many mimetite and pyromorphite specimens are nearly indistinguishable. Both are six-sided crystals that come in colors like yellow, orange, brown, and green. They are brittle with similar levels of hardness and transparency. Energy-Dispersive X-ray Spectroscopy (EDS) was performed on this specimen using a Scanning Electron Microscope (SEM) which found levels of O (oxygen), Pb (lead), Cl (chlorine), and P (phosphorus) consistent with pyromorphitePb5(PO4)3Cl. Mimetite is Pb5(AsO4)3Cl.
See Pyromorphite Zambia on display in Hillman Hall of Minerals and Gems in the Systematic Collection.
Photo by Debra Wilson, Collection Manager, Section of Minerals