Pargasite: Gemstone Information
Pargasite is NaCa2(Mg4Al)Si6Al2O22(OH)2 and forms stout prismatic crystals of the monoclinic system with twinning frequent and a perfect cleavage in one direction. The hardness is 5–6 and the SG 3.04–3.17. Crystals are transparent to translucent bluish green or chrome (emerald)- green to light brown. The RI for the alpha, beta and gamma rays is 1.613–1.65, 1.618–1.66 and 1.635–1.67, biaxial positive with birefringence 0.022. Pleochroic colours include colourless, light brown, bluish green and greenish yellow. Pargasite, a member of the amphibole group, occurs in igneous and metamorphic rocks and fine emerald-green crystals have been found in the northern areas of Pakistan; some have been faceted.