Chrysoprase from Warrawanda, western Australia

Chrysoprase from Warrawanda, West Australia, was observed using optical and transmission electron microscopies (TEM), Fourier transformation infrared spectroscopy (FT-IR) and electron microprobe analyses (EPMA). It was tried to identify origin of the green colour. TEM observations and IR-spectra analyses show that the chrysoprase includes kerolite, which occurs as a cotton-like aggregate of extremely fine-grained crystals at the boundaries of quartz grains and in quartz crystals. EPMA analyses show that the kerolite contains about 10 wt % NiO, and that NiO content of the chrysoprase increases with the degree of silicification of the surrounding serpentinite. The Ni-bearing kerolite derived from the silicified serpentine is inferred to cause the green colour of the chrysoprase.