Part III. Of Stones Irregular. 315 
CHAP. VI. 
Of STONES IKREGVLAR. 
AS GEMS are chiefly diftinguifhed by their Colours, 
and all other Stones Regular, by their Figures : So 
thefe, by the different degrees of Hardnefs. 
EMERY. Smirk. Of a kind of blackilh Iron-colour. 
The harden 1 of un figurd Stones. And is therefore ufed 
for the polifhing and cutting of all Gems, except the Dia- 
mond. For the hollowing of flinty Mortars, together with 
Sand, (a) For the brightening of Armour, and all Metal- $J$ a *iid 
lick. Equipage. And for Moulds or Forms for the cafting . 
of Medals and other Coins. Yet Mr. Boyle (b) hath open'd & Of'Gmri 
it with a Corrofive Menftruum fo far,as to make an infufion p " j6 °' 
of Galls therewith to turn blackifh. 
A FLINT of the colour of yellow Amber. Italludeth 
to a Topaz. 
A polilh'd FLINT, not unlike a Calcedony. 
A rough FLINT naturally perforated with feveral large 
Cavities running one into another. It feems to be an aflay 
towards an Eagle-Stone, which is commonly a Flint 
Flints are of all colours. Some fo clear, thatfome Jew- 
elers cut and fell them for Bohemick Diamonds, (c) They fr) Boet - de 
are alfo ufed for factitious Gems,with the mixture of Metals, em " 
in fufion. For making of Glafs. For Mortars for the 
powdering of the Fragments of Gems. And fometimes added 
to melted Metals, to keep them,as is fuppofed,by the Metal- 
lifts, from fpending. (d) (J) AmbroC 
A BALL of SERPENTINE MARBLE 5 called Ophites, ^mTcIl 
from the winding of the Veins. Near four inches in Dia- 
metre. Of the nobleft fort 5 confining of White, and Red 
or Murrey Veins, in Black. • • • 
ANOTHER MARBLE-BALL, two inches and * m Dia- 
metre,Veined,and fpoted with Red,Sand-colour,and White. 
A THIRD, Veined and fpoted with BlacL.Sand-colour d, 
and White. 
A Ball of ONYCHINE MARBLE,about the fame big 
nefs 3 on one fide Sand-colour d, on the other Grey. That 
which is obfervable is this, That inftead of winding Veins, 
S f 2 if 
