74 This metal Guanin is the Orichalc of the ancient Greeks; which has so much puzzled the learned, being wrongly deemed Platina, which would have been Infusible.
"The American Nations, Vol. I."
C. S. Rafinesque
Compounds of Al are very Infusible and difficult of reduction.
"An Introduction to Chemical Science"
R.P. Williams
Under the blowpipe, zircons are Infusible, but the coloured stones when heated strongly become heavier, and as they are contracting, their colour fades, sometimes entirely, which changes are permanent, so that as they possess the adamantine lustre, they are occasionally cut like a diamond, and used as such, though their deficiency in fire and hardness, and their high specific gravity, make them readily distinguishable from the diamond.
"The Chemistry, Properties and Tests of Precious Stones"
John Mastin