C 53 ° 3 
XXXIV. On the Cryjiallizations obferved on Gb/s, By 
James Keir, Ef quire , of Stourbridge. Communicated 
by G. Fordyce, M. D. F. R. S, 
^ a 7 y 6 23> r f ^ H E peculiar figure of rock- cry fial has 
jL been long obferved. Many other fub- 
ftances, as fpars, precious Hones, pyrites, ores, metals r^, 
falts, waters;, and oilfD, are alfo known to affe6t an uni- 
formity of lliape, when they are expofed to certain de- 
grees of heat, cold, fluidity, and other neceflary circum- 
ltances. From their refemblance in this refpe£t to rock- 
cryftal, they are faid, when they aflume their peculiar 
forms, to cryilallize; and the regularly-fliaped bodies, 
into which thefe fubftances concrete, are alfo called 
cry Hals. 
(a) Native gold has been found in a cryftallized form. M. rome de 
l’isle, in his EJfa'i de C r yjl alio graphic, p. 39O, fays, that he has feen pieces of 
native gold which were eight- tided folids, like cryftals of allum, and one pices 
which was an hexagonal plate. In Dr. hunter’s mufeum, l'ome fine fpccimens 
of cryftallized native gold are to be feen. Gold may be cryftallized by art alfo. 
Some aether having b«en poured into a folution of this metal in aqua regia , 1 
obferved, a few months afterwards, the gold lcparatcd from the mcnjlruum , in the 
form of diftinft polygonous prifins. 
(b) The various and regular forms of the particles of fnow, which is 
nothing elfe than water cryftallized, are well known. 
(c) The cryftals, formed by cold, in the oil of faflafras, have been obferved 
to be very beautiful, regular, hexagonal prilms. 
Ill 
