A jadeite material has a thickness in excess of about 1.0 mm and CIELAB indices
of L*42, a*<-;6, and b*+6. The grain size of the jadeite material is
less than about 30 microns and is an equiaxed grain structure. The jadeite material
has an optical transmission peak between 500 and 565 nm with an I/IO
optical transmission ratio of over 40%. The first step in making the jadeite material
is to wrap a glass block, convertible by HP/HT into jadeite and having a nominal
composition of NaAlSi2O6, with a graphite or refractive metal
sheet. The wrapped glass block is placed in an HP/HT apparatus, rapidly heated,
and subjected therein to a pressure in excess of about 3 GPa and a temperature
in excess of about 1000 C. for a time adequate to convert the glass block
into jadeite. The jadeite material then is cooled and the pressure subsequently released.
