A vertical crucible called a "skull" is used to make the gem called "cubic" this
[DOC] [TLE] Spring 1981 Gems & Gemology - GIA [PAR] Nov 9, 1975 ... plays in dealing with gem materials, we have used color photographs ... lished 
we have called upon many of the prominent figures in the gemological 
community to serve on ..... which is markedly striated vertically to the .... of melting 
the material without a crucible to ob- .... Half of a large skull of yellow cubic.