The mines, which have been constructed for the purpose of working quartz lodes containing gold, are very extensive, and argue a high stage of civilization possessed by the ancient miners.
Gold is obtained chiefly from quartz reefs, but there are still some important alluvial deposits being worked.
The greatest development of quartz reefing is found in Victoria, some of the mines being of great depth.
Jacquerod and Perrot have found that quartz-glass is freely permeable to helium below a red-heat (Comet.
Of the quartz-monzonite type are the whitish granites of Bethel and Rochester (Windsor county) and Randolph (Orange county), the light grey of Dummerston (Windham county), and the darker greys of Cabot (Washington county), Derby (Orleans county), Hardwick and Groton (Caledonia county) and Topsham (Orange county).
Well-worn pebbles of amorphous quartz (agate, chalcedony, jasper, &c.) are found in the stratified drift along the western side of the Tertiary region of the state, and from Columbus northward.
The quartz-schists consist of quartz and white mica, and are intimately related to quartzites.
The prevailing formations appear to be granites which are veined with white quartz, and underlie old sedimentary brown sandstone and limestone formations.
From quartz mines.
In East Siberia gold is obtained almost exclusively from gravel-washings, quartz mining being confined to three localities, one near Vladivostok and two in Transbaikalia.
Galena occurs in veins in the Cambrian clay-slate, accompanied by copper and iron pyrites, zinc-blende, quartz, calcspar, iron-spar, &c.; also in beds or nests within sandstones and rudimentary limestones, and in a great many other geological formations.
The conglomerates consist almost entirely of pebbles of quartz set in a hard 2 At the Standerton gauge on the Vaal in 1905-1906, a year of extreme drought, the total flow was 8,017,000,000 cub.
The company also owns iron mines, limestone and quartz quarries, large iron-works at Domnarfvet and elsewhere, a great extent of forests and saw-mills, and besides the output of the copper mines it produces manufactured iron and steel, timber, wood-pulp, bricks and charcoal.
The Upper Devonian was a period of marine retreat; the crustal disturbances of the Lower Devonian were renewed and great quartz-pebble beaches were formed on the rising shore lines, producing the West Coast Range conglomerates of Tasmania, and the similar rocks to the south-east of Mansfield in Victoria.
The lodes occur in Silurian metamorphic micaceous schists, intruded by granite, porphyry and diorite, and traversed by numerous quartz reefs, some of which are gold-bearing.
Molybdenum, in the form of molybdenite (sulphide of molybdenum), is found in Queensland, New South Wales and Victoria, associated in the parent state with tin and bismuth in quartz reefs.
He passed the oscillations to be detected through a fine wire or strip of gold leaf, and over this, but just not touching, suspended a loop of bismuth-antimony wire by a quartz fibre.
In the south the body is slightly cut by women with small flakes of glass or quartz in zigzag or lineal patterns downwards.
AMETHYST, a violet or purple variety of quartz used as an ornamental stone.
On exposure to heat, amethyst generally becomes yellow, and much of the cairngorm or yellow quartz of jewellery is said to be merely "burnt amethyst."
Purple corundum, or sapphire of amethystine tint, is called Oriental amethyst, but this expression is often applied by jewellers to fine examples of the ordinary amethystine quartz, even when not derived from Eastern sources.
There is a considerable export of quartz crystal, commercially known as "Brazilian pebbles," used in optical work.
The difference between schists and gneisses is mainly that the latter have less highly developed foliation; they also, as a rule, are more coarse grained, and contain far more quartz and felspar, two minerals which rarely assume platy or acicular forms, and hence do not lead to the production of a fissile character in the rocks in which they are important constituents.
In the mica-schists of this group biotite or muscovite may be the principal mineral and often both are present in varying proportions; the mica has developed from the argillaceous matter of the original rock; in addition there is always quartz and sometimes felspar (albite or oligoclase).
The phyllites (q.v.) form a middle term between this group and the slates; they consist usually of quartz, white mica and chlorite, and have much of the foliation and schistosity of the mica-schists.
Often they contain quartz and felspar, sometimes pyroxene, amphibole, garnet or epidote.
Some of the "porphyroids" which have grains of quartz and felspar in a finely schistose micaceous matrix are intermediate between porphyries and micaschists of this group. Still more numerous are orthoschists of hornblendic character (hornblende-schists) consisting of green hornblende with often felspar, quartz and sphene (also rutile, garnet, epidote or zoisite, biotite and iron oxides).
The granite (biotite, biotite-muscovite and quartz-monzonite) is of fine quality, and has been used extensively in the United States for building and monumental purposes; and the burning of lime is by far the most important industry of the city.
Dennstedt, which was first proposed in 1902, the substance is vaporized in a tube containing at one end platinum foil, platinized quartz, or platinized asbestos.
Celts, of the usual late neolithic type, were generally of green jasper; hoe-blades (looking almost exactly like palaeolithic haches a main) of chert or coarse limestone; hammers of granite; mace-heads, of identical type with the early Egyptian, of diorite and limestone; nails of obsidian or smoky quartz, often beautifully made.
On the under-side, there are found attached fragments of limestone and quartz, showing that the shingle bed once extended up to it, and that it then formed the original floor.
The Eastern Andes is a magnificent range in the southern part of Peru, of Silurian formation, with talcose and clay slates, many quartz veins and eruptions of granitic rocks.
The product has a brilliant white fracture, a specific gravity of 4.87, very friable, but harder than quartz or steel.
The quartz reefs which crop out in the granite ranges of the Tehama contain traces of gold.
It may also be accompanied by pyrites, galena, arsenides and antimonides, quartz, calcite, dolomite, &c. It is widely distributed, and is particularly abundant in Germany (the Harz, Silesia), Austro-Hungary, Belgium, the United States and in England (Cumberland, Derbyshire, Cornwall, North Wales).
Sand consists of grains of quartz or flint, the individual particles of which are large enough to be seen with the unaided eye or readily felt as gritty grains when rubbed between the finger and thumb.
Chemically pure sand is silicon dioxide (SiO 2) or quartz, a clear transparent glass-like mineral, but as ordinarily met with, it is more or less impure and generally coloured reddish or yellowish by oxide of iron.
In Germany very similar filters have also been used, pearl-quartz gravel taking the place of coral sand, which it closely resembles.
It is found in the form of oxide (silica), either anhydrous or hydrated as quartz, flint, sand, chalcedony, tridymite, opal, &c., but occurs chiefly in the form of silicates of aluminium, magnesium, iron, and the alkali and alkaline earth metals, forming the chief constituent of various clays, soils and rocks.
Electrical furnaces have not as yet been employed for ordinary glass-making on a commercial scale, but the electrical plants which have been erected for melting and moulding quartz suggest the possibility of electric heating being employed for the manufacture of glass.
There is a gold mine at Kyaukpazat in the Mawnaing circle of the Kathra district, where the quartz is crushed by machinery and treated by chemical processes.
A quartz vein or bed of hard rock may show itself as a sharp ridge or as a well-defined bench; a stratum of soft rock or the line of a great fissure, or the weakening of the strata by an anticlinal fold, may produce a ravine or a deep valley.