Not required for students of EPS 2
Chrysophrase is Ni-bearing chalcedony (fibrous var. of quartz). Ni contents range from a few tenths to a few weight percent. Ni is probably in Ni compounds (e.g., garnierite) mixed in with the silica. It may contain a mixture o tridymite and cristobalite. Brooks (1965) described chrysoprase in laterites overlying Ni-containing serpentines in Qld. See Heflik et a. (1989) for a review of some mineralogical and color properties. Most chrysophrase comes from Australia.
Brooks JH (1965) Marlborough Creek chrysophrase deposits, Rockhampton district, central Queensland. Gems and Gemology, 11 323-330, 351.
Heflik et. al. (1989) Colour of chrysophrase in light of mineralogical studies. Australian Gemologist, 17: 43-46, 58-59.