Clear
Quartz, or " Rock Crystal," contains forty-six per cent of Silicon, and
fifty-three per cent of Oxygen. It is found in almost every part of the
globe. Sometimes the Crystal embodies an admixture of Mica, Rtttile,
Tourmaline, Topaz, Asbestos, Bitumen, and certain other foreign
matters; with the occasional presence of a greenish mineral—"
Chlorite,"—a stone, or " pebble " used by opticians for making the
lenses of spectacles, because of its superior hardness, and durability;
in preference to glass, for its coolness, uncommon with most other
precious stones. Formerly in this country the Crystal was powdered for
medicinal use, being given, mixed with wine, in cases of dysentery ;
likewise pieces were held against the tongue for assuaging fever, and
to slake thirst. Many of the red, green, and brown colours shown by
members of the Quartz group are due to manganese, and oxides of iron.
Traces of water, alumina, lime, and magnesia, also occur. Silex
(Silicon) is never found free, but always united, either with oxygen,
as " silica" (Rock Crystal), or with oxygen, and one or other of the
metals, forming silicates of such metals. As a secret means of
poisoning, the Hindus have a powdered glass, which they contrive
unsuspectedly to mix with what the victim drinks, until a fatal
intestinal irritation is set up.
" Glass was first found "—(Bartholomew Anglicus, On the Properties of Things—1250)
" by Ptolomeida, in the cliff beside the river that is called Vellus,
that springeth out of the foot of Mount Carmel, at which shipmen
arrived." For, " upon the gravel of that river shipmen made fire of
clods medlied with bright gravel; and thereof ran bright streams of new
liquor that was the beginning of Glass." " But long time previous
