f* A R T III. 
Of Gems. 
289 
The EMBRIO of an ONTX. So I name it. ’Tis a half 
Globe., polifh’d. The outer Cruft or Shell, Semiperfpicuous, 
and as hard as of a true Oynx. The part within, round, of 
an opacous liver-colour, and fo foft as to be diftoluble with 
Spirit of Nitre. 
A PEBBLE of kin to the Onyx. ’Tis round or globous, 
and on the two oppofite Tides, a little prominent. About 
an inch in Diametrc. The outer Shell, yellowifh 3 the mid- 
dlemoft, red 3 both opacous. The intimate Part, diapha¬ 
nous, and oi the colour of a glowing Coal. It feemeth to 
me, That as Tome Pebbles , fo many more Flints, arc a fort 
of ONTX. The Onyx, amongft other things, is ufedfor the 
making of Cups 5 of which, King Mithridates is faid to 
have had twoThoufand. Sometimes fo big, as to ferve 
for Statues. At Rome , in the Bafilica of St. Peter , there are 
( or were in Boetius’s time) fix little Onychine Columns. (<*)<» Boet.uk 
They grow both in the Eaft and Weft-Indies , and in 2 -deGem. 
Europe. & L ' 
The ONYCHATE. Betwixt an Onyx and an Achate. 
Compofed not of Zones , or Balls ,but of Plates, perfpicuous 
and afh-colour’d, mixed. 
ANOTHER, of a Globous Figure, confiding of Plates 
afh-colour’d and brown: like a little turn’d Bowl of AJh- 
vtood. 
A THIRD, confiding of Black , and Horn-colour'd 
Plates , mixed together, thefe latter, being alfo ftained with 
red fpots. 
The PSEUDOPALUS. ’Tis of a pale blewifh Water, 
like a Fijhes Eye, or a drop of S/fmd-Mil/y, with fome 
Rays of yellow. 
ANOTHER, growing to a thin Cruft or Matrix of an 
Iron-colour. 
This, and the Opalus itfelf, the fofteft of Gems. (i)They Wfioet.de 
are now found principally in Hungary, (c) The Opalus, ^™x a , erm 
faith Boetius, hath its variety of colours, only by Re- Voyages. 
fraction : (adds Laet, (d) like thofe in a Prifme) for if it be (j) Lib. 1. 
broken it loofeth them.’Tis true,that thefe colours are pro- dc Gcm - 
duced by Refraction :yet not as in a Prifme 5 as not depend - c ' 13 ‘ 
ing upon the Figure, (for they will not be produced in 
other Stones of the fame figure) nor fo much as any flaw 
orflakinefs in the Stone 5 but its peculiar Texture, which 
P p caufeth 
