MINERALOGY. . .% 
There is, however, another of the fame 
kind in Sweden, which by rededlion ap- 
pears rather brown ^ but by refradion is 
red, with violet veins. 
The white opal. Its ground is white, of 
a glafs-like complexion, from whence 
are thrown out green, yellow, and bluifa 
rays; but it is of a reddifli or rather flame 
colour, when held agalnfl: the light. 
I. Of many colours. The oriental opal, 
2 . Of a milky colour % from Eibenftock, 
in Saxony. 
3. Bluifli, and femi-tranfparent. This is 
not fo much valued, as thofe which are 
* i have lately got afmall piece of pfeudo- agate, from the 
Eaft-lndies, which is of a yellowilh brown, and pale blue, or 
rather milky colour, with a ffiining brightnefs, exaftly like 
that of the milky opals of this fedion, and received alfo forae 
other fpecimens found at St. Georgio, near Turin, in 
Piedmont, there called by the name, Pfeudo agate (Baftard 
agate), a name which feems very well adapted to this 
Hone, iince in every refpedl, hardnefs excepted, it comes 
neareft to the agates ; becaufe, i . it is tranfparent in the fame 
degree as agates, and varied with red and grey cclours, inter- 
fperied fonietimes with white opaque veins, or rings, and 
black dendriticai figures, z . It is of a very fine and iliining 
texture, when broke, rather fuperior to that of the agates, but 
fo foft, that it fcarce yields ahy fparks, when ftruck againft 
Heel; and does not admit of any polifh, but what is inferior 
to the luflre of it3 natural texture : however, it flightly marks 
common window glafs. 3 When broke through the den» 
drites, it is as fmOoth and fliining at that place as in any 
other ; and thefe dendrites vanifh in the fire, without leaving 
any pores in the Hone. 4. It does not melt before the flamej 
by the blow-pipe, but becomes perfedly white and <^aqtre„ 
5, Nor is it fufible even with borax. 6. It does not ferment 
with the acid of nitre. . 
Some- 
