Yellowish green diopside and tremolite from Merelani, Tanzania

Four similar-appearing yellowish green samples from Block D at Merelani, Tanzania, were identified as diopside and tremolite. The gems are identical in color, but their standard gemological properties are typical for calcic pyroxene and amphibole. The identification of the diopside was made with Raman spectroscopy, while single-crystal X-ray diffraction and electron-microprobe analyses were used to confirm the amphibole species as tremolite. Absorption spectroscopy (in the visible-mid-infrared range) revealed that the two gem materials are colored by V³⁺, Cr³⁺, or both.