Chrysoprase from Warrawanda, West Australia, was observed using optica
l 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 observation
s and IR-spectra analyses show that the chrysoprase includes kerolite,
which occurs as a cotton-like aggregate of extremely fine-grained cry
stals at the boundaries of quartz grains and in quartz crystals. EPMA
analyses show that the kerolite contains about 10 wt % NiO, and that N
iO content of the chrysoprase increases with the degree of silicificat
ion of the surrounding serpentinite. The Ni-bearing kerolite derived f
rom the silicified serpentine is inferred to cause the green colour of
the chrysoprase.