"Chalcedony is the name given to compact varieties of silica
which comprise minute quartz crystals with sub-microscopic pores.
There are two main varieties: chalcedony, which is uniformly coloured,
and agate which is characterised by curved bands or zones of differing
colour."
(Hamilton et al 1976, 130).
It has conchoidal fracture and therefore has the same knapping
qualities as flint.
flint, chert,
carnelian, and jasper are all varieties
of chalcedony.
