The rocks are probably of quartz, i.e.
Gold is obtained chiefly from quartz reefs, but there are still some important alluvial deposits being worked.
Jacquerod and Perrot have found that quartz-glass is freely permeable to helium below a red-heat (Comet.
The greatest development of quartz reefing is found in Victoria, some of the mines being of great depth.
Often they contain quartz and felspar, sometimes pyroxene, amphibole, garnet or epidote.
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.
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).
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."
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.
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.
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.
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 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.
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.
Deep, and then through a series of remarkable underground caves hollowed out of a quartz mountain and, with their arches and white columns, presenting the appearance of a pillared temple.
Few obsidians are entirely vitreous; usually they have small crystals of felspar, quartz, biotite or iron oxides, and when these are numerous the rock is called a porphyritic obsidian (or hyalo-liparite).
These crystals have, as a rule, very good crystalline form, but the quartz and felspar are often filled with enclosures of glass.
Occasionally the rounded cracks extend from the matrix into some of the crystals especially those of quartz which have naturally a conchoidal fracture.
A dull stony-looking rock results, the vitreous lustre having entirely disappeared, and in microscopic section this exhibits a cryptocrystalline structure, being made up of exceedingly minute grains principally of quartz and felspar.
Gold-mining and quartz-mining are its principal industries, and in 1907 Nevada county's output of gold (104,J90.76 oz., worth $2,162,083) was second only to that of Butte county (134,813.39 oz., worth $2,786,840) in California; the county is the leading producer 1 Died the 21st of September, 1890, and Frank Bell became governor by virtue of his office as lieutenant-governor.
From quartz mines.
In West Siberia, however, quartz-mining is steadily increasing in importance: whereas in 1900 the output of gold from this source was less than 10,000 oz., in 1904 it amounted, to close upon 50,000 oz.
The districts of Mariinsk and Achinsk are the most successful quartz-mining localities.
Lastly, from the Altai region, as well as from the Nerchinsk Mountains, precious stones, such as jasper, malachite, beryl, dark quartz, and the like, are exported.
Flattened crystals of garnet, films of quartz, and needles of tourmaline are not uncommon.
These veins consist of felspar, quartz and mica, often with smaller amounts of other crystallized minerals, such as tourmaline, beryl and garnet; they are worked for mica in India, the United States (South Dakota, Colorado and Alabama), and Brazil (Goyaz, Bahia and Minas Geraes).
Besides the alluvial deposits a little mining is carried on, gold being present in the thin veins of quartz which cross the sandstone.
Throughout the world, primary deposits of tinstone are in or closely connected with granite or acid eruptive rocks of the same type, its mineral associates being tourmaline, fluorspar, topaz, wolfram and arsenical pyrites, and the invariable gangue being quartz: the only exception to this mode of occurrence is to be found in Bolivia, where the tin ore occurs intimately associated with silver ores, bismuth ores and various sulphides, whilst the gangue includes barytes and certain carbonates.
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.
At Bendigo in Australia are several shafts between 3000 and 4000, and one, the Victoria Quartz mine, 43 00 ft.
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.
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.
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.
In Germany very similar filters have also been used, pearl-quartz gravel taking the place of coral sand, which it closely resembles.
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.
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).
The quartz reefs which crop out in the granite ranges of the Tehama contain traces of gold.
The product has a brilliant white fracture, a specific gravity of 4.87, very friable, but harder than quartz or steel.
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.
Pharmacosiderite is a mineral of secondary origin, the crystals occurring attached to gozzany quartz in the upper part of veins of copper ore.
Veins of amethystine quartz are apt to lose their colour on the exposed outcrop.
There have been repeated stories of diamonds obtained from the Finley Mountains (which are volcanic) in the central province, but all specimens sent home, except one, have hitherto proved to be quartz crystals.