Part III. Of Gems. 289 
The EMBRIO of an ONTX. So I name it. Tis ahalf 
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 diffoluble with 
Spirit of Nitre. 
A PEBBLE of kin to the Onyx, - 'Tis round or globous, 
and on the two oppofite fides, a little prominent. About 
an inch in Diametre. The outer Shell, yellowifh 5 the mid- 
dlemolt, red 5 both opacous. The intimate Part, diapha- 
nous, and of the colour of a glowing Coal. It feemeth to 
me, That as fome Pebbles, fo many more Flints, are a fort 
of ONTX. The Onyx, amongft other things, is ufed for the 
making of Cups 5 of which, King Mithridates is faid to 
have had two Thoufand* Sometimes fo big, as to ferve 
for Statues. At Rome, in the Bafilica of St. Peter, there are 
( or were in Boetiuss time ) fix little Ony chine Columns, (a) ( a ) Boet.iib* 
They grow both in the Raft and Weft-Indies , and in 2 - de Gem. 
Europe. L * 
The ONYCHATE. Betwixt in Onyx and an Achate. 
Compofed not of Zone s, or Balls,b\it of Plates, perfpicuous 
and aih-colour'd, mixed. 
ANOTHER, of a Globous Figure, eonfifting of Plates 
afecolourd and brown : like a little turn d Bowl of Afb- 
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 blewiih Water, 
like a Fifbes Eye, or a drop of S kjni d-Mill^i with fome 
Rays of yellow. 
ANOTHER, growing to a thin Cruft or Matrix of an 
Iron-colour. 
: This, and the Opalus it felf, the fofteft of Gems, (b) They 0>) Boa. ie 
are now found principally in Hungary, (c). The Opalus, ^ m j atern 
faith Boetius, hath its variety of colours, only by Re*^gex. 
fraction : (adds Laet, (d) like thofe in a Prifme) for if it be (j) Lib. u 
broken it loofeth them. 'Tis true,that thefe colours are pro- dc Gem * 
duced by Refraction :yet not as in a Prifme 5 as not depend- c * * 3 ° 
ing upon the Figure, ( for they will not be produced in 
other Stones of the fame figure ) nor fo much as any flaw 
or flakinefs in the Stone $. but its peculiar Texture, which 
lii Pp caufeth 
