but the smallest specks that I could find among well ground _Vermilion_ and
_Red-lead_, seem'd to be a Red mass, compounded of a multitude of less and
less motes, which sticking together, compos'd a bulk, not one thousand
thousandth part of the smallest visible sand or mote.

And this I find generally in most _Metalline_ colours, that though they
consist of parts so exceedingly small, yet are they very deeply ting'd,
they being so ponderous, and having such a multitude of terrestrial
particles throng'd into a little room; so that 'tis difficult to find any
particle transparent or resembling a pretious stone, though not impossible;
for I have observ'd divers such shining and resplendent colours intermixt
with the particles of _Cinnaber_, both natural and artificial, before it
hath been ground and broken or flaw'd into _Vermilion_: As I have also in
_Orpiment_, _Red-lead_, and _Bise_, which makes me suppose, that those
_metalline_ colours are by grinding, not onely broken and separated
actually into smaller pieces, but that they are also flaw'd and brused,
whence they, for the most part, become _opacous_, like flaw'd Crystal or
Glass, &c. But for _Smalts_ and _verditures_, I have been able with a
_Microscope_ to perceive their particles very many of them transparent.

Now, that the others also may be transparent, though they do not appear so
to the _Microscope_, may be made probable by this Experiment: that if you
take _ammel_ that is almost _opacous_, and grind it very well on a
_Porphyry_, or _Serpentine_, the small particles will by reason of their
flaws, appear perfectly _opacous_; and that 'tis the flaws that produce
this _opacousness_, may be argued from this, that particles of the same
_Ammel_ much thicker if unflaw'd will appear somewhat transparent even to
the eye; and from this also, that the most transparent and clear Crystal,
if heated in the fire, and then suddenly quenched, so that it be all over
flaw'd, will appear _opacous_ and white.