QUARTZ.
Of this very common mineral, it is only necessary to notice the varieties which are rare, and which more particularly comprise those that present peculiarities of colour.
Pol Ewe and Loch Greinord, on the western coast of Scotland. This is found in gneiss, forming veins, and the smell often resembles that of putrid sea weed. It is sensible only on friction, and diminishes when the specimens have been so long kept as to lose their water.
Green. Coloured by chlorite. In Bute ; on the shore of Cowal; on the south-eastern shore of Jura, and on the north-western of Isla, opposite. This quartz forms veins in chlorite schist; and is always ac companied by common chlorite. Some of the va rieties are so dark as to be nearly black. It has been mistaken for prase, from which it is essentially dif ferent. The following variety is the prase of the Germans.
Green. Coloured by green actinolite. Prake. I have found this variety only once, and it was in a very limited quantity even there. This was in a small isl and within, and not far from the entrance of Loch Hourn. As it is too insignificant to have a name in the map, I cannot direct mineralogists to it more ac curately. This quartz is in veins, traversing actino lite schist; and, according to the quantity of the in termixed colouring matter, it varies from a very light to the usual dark green of this mineral.
Green. Coloured by the green earth of the trap rocks. In Rum, in Scuir-more, together with the he liotrope of that place. In Glen Farg, and in the hill of Kinnoul. It also occurs in _Ayrshire; and general ly, in this case, it is intermixed with other chalcedo nies and agates.
Green. Coloured by an intermixture of green com pact felspar. In Rona, (East) at Pol Ewe, and on va rious parts of the western coast of Ross-shire.
Pink. Opaque, and pink or flesh-coloured. Com mon quartz, coloured by an unknown ingredient. In Lewis, from gneiss.
Pink. Opalescent, or rather milky. In Coll; in Aberdeenshire, on the Buck of Cabrach. The latter specimens are nearly transparent. In Loch Maddy in North Uist.
Brown red. Transparent. Apparently coloured by iron. On the western coast of Sutherland, in veins traversing gneiss, between Loch Inver and the Ru Storr. In East Rona; in the Angus hills.
Brown red. Milky or chalcedonic quartz. At Gair loch in Ross-shire, in gneiss.
Purple or lilac. Opaque. near Selie voe, in gneiss.
T'iolet blue. Pale; opalescent. In Loch Maddy,
in North Uist, in gneiss.
Purple. Crystallized; amethyst. In trap in the hill of Kinnoul, and elsewhere; found in the centre of agate nodules. In the hills of Mar, in granite.
Grey. Blue or French grey. Opaque. In Glen Tilt, in veins in gneiss; and in Aberdeenshire.
Grey. Blackish. Common quartz, irregularly transparent. In various parts of Aberdeenshire, and in Shetland.
Grey. Blackish. Chalcedonic quartz. In Gairloch, in Ross-shire; on Ben Lair in the same county, in gneiss. The colour varies from very pale to very dark blackish grey, and the specimens are also exceed ingly various in their degrees of transparency.
Black. Common transparent quartz,apparently co loured by an intermixture of hornblende, just as it is sometimes coloured green by actinolite. The fine splinters are translucent. In Ben Lair, in Ross-shire, in hornblende schist; but it seems very rare.
Brown. Transparent quartz. The colour varies in intensity, but the colouring ingredient is not known. It is discharged by a moderate heat. It is found crys tallized, notedly in Cairngorm, in granite. In Arran, and in Benna-Chie, in granite. In St. Kilda, in that syenite which is connected with augite rock and green stone. At Killin, perfectly transparent, but uncrys tallized; in nodules in chlorite schist. In North Rona, in granite veins, uncrystallized.
Yellow. A brownish yellow crystal occurs in the hills of Mar. Yellow quartz, imperfectly transparent and full of fissures, is not uncommon in the Perthshire hills, but it seems in general to have been coloured somewhat recently, by having admitted a stain from the rust of iron.
Colourless or greenish. White amethyst. In Fife, and in the hill of Kinnoul.
Colourless. Transparent. The crystallized kind is too common to deserve notice; but as it is rarely trans parent when in veins and nodules, I may here remark that it occurs in this manner in the chlorite schist, at the south-eastern extremity of Jura, and the north eastern of Isla.
Granular white quartz, resembling refined sugar, is found in Harris, and in Ben Lair, in veins traversing gneiss. There is here also found a singular variety, in which a purely hyaline quartz passes gradually into this snow-white and finely granular kind. It is unne cessary to point out the localities of the other varieties, which abound everywhere.