Part 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 fort as to be dilToluble with 
Spirit of Nitre. 
A PEBBLE of kin to the Onyx. 'Tis round or globous* 
and on the two oppofitc fides, 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 of the colour of a glowing Coal. It feemeth to 
me, That as fome Pebbles, fo many more Fl'mts, are a fort 
of ONTX. The Onyx, amongft other things, is ufed for th£ 
making of Cups 3 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 Bcetims time ) fix little Ony chine Columns, {a) ^ Boet.lik 
They grow both in the Eaft and Weft-Indies, and in s.deGem. 
Europe. 
The ONYCHATE. Betwixt an Onyx and an Achate . 
Compofed not of Zones, or Balls,but of Plates, perfpicuous 
and alh-colour d, mixed. 
ANOTHER, of a Globous Figure, confiding of Plate s 
afti-colour'd and brown : like a little turn'd Bowl of Ajh- 
wood. 
A THIRD, confiding of Black , and Horn-colourd 
Plates, mixed together, thefe* latter, being alfo ftained with 
red fpots. 
The PSEUDOPALUS. 'Tis of a pale blewifti Water, 
like a Fifbes Eye, or a drop of Skimd-Milk^, with fome 
Rays of yellow. 
ANOTHER, growing to a thin Cruft or Matrix of an 
Iron-colour. 
This, and the Opalw itfelf, the fofteft of Gems, (b) They 0>) Boct.de 
are now found principally in Hungary, (c) The Opalus, (^"ramn 
faith Boetius , hath its variety of colours , only by Re- Voyages* 
fradion : (adds Laet, (d) like thofe in a Prifme) for if it be ^ Lib. u 
broken it loofeth them. J Tis true,that thefe colours are pro- de Gem ° 
duced by Refraction :yet not as in a Prifme 5 as not depend- c ' 130 
ing upon the Figure, ( for they will not be produced in 
other Stones of the fame figure ) norfo much as any flaw 
or flakinefs in the Stone 3 but its peculiar Texture, which 
P p caufeth 
