United States or Czechia ? Vote for the TOP Country of the Week !
From this place to the mines the rocks were soft decomposing dolerites, with many harder bands of felsite, and, occasionally, plains composed of more recent trachytic lavas. We passed through another weedy, dilapidated town, called Condego, where they have a singular custom at their annual festival held on the 15th of May.
This division corresponds with that proposed by Bunsen and Durocher for volcanic rocks, upon the results of analyses of a large number of specimens from various districts. Examples: Basalt, Dolerite, Hornblende rock, Diorite, Diabase, Gabbro, Melaphyre, and Leucite lava. Examples: Trachyte, Rhyolite, Obsidian, Domite, Felsite, Quartz-porphyry, Granite.
Bostonians who know their geology should feel at home in Nantucket, for, while it is superficially allied to Cape Cod, the pebbles of the stratified gravel on the north being in a large part derived from the group of granite rocks known on the neighboring mainland, perhaps half of the mass being of that nature, the remainder is of the felsite and felsite-porphyries so common in the region about Boston.
During my investigation on the ore of the Deep Creek mines, Nambucca, New South Wales, I have found in them what I believe to be gold existing as a natural sulphide. The lode is a large irregular one of pure arsenical pyrites carrying, in addition to gold and silver, nickel and cobalt. It exists in a felsite dyke immediately on the coast.
Similar masses occur in North Mayo, south of Belderg Harbour. Cambrian Period. In the Pass of Llanberis, along the banks of Llyn Padarn, masses of quartz-porphyry, felsite and agglomerate, or breccia, indicate volcanic action during this stage. These rocks underlie beds of conglomerate, slate and grit of the Lower Cambrian epoch, and, as Mr.
Excavations have brought to light more than six hundred celts or knives, generally of smaller size than those found in Denmark or France. Rock of many kinds, including serpentine, schist, felsite, jadeite, diorite, and nephrite, were used; and saws of flint or chalcedony, some toothed on one side only, others on both, are of frequent occurrence.
Quartz, dense and milky, also in quartz of nearly every colour and appearance, saccharoidal, crystalline, nay, even in clear glass-like six-sided prismatic crystals, and associated with silver, copper, lead, arsenic, iron as sulphide, oxide, carbonate, and tungstate, antimony, bismuth, nickel, zinc, lead, and other metals in one form or another; in slate, quartzite, mica schist, granite, diorite, porphyry, felsite, calcite, dolomite, common carbonate of iron, siliceous sinter from a hot spring, as at Mount Morgan; as alluvial gold in drifts formed of almost all these materials; and once, perhaps the most curious matrix of all, a small piece of apparently alluvial gold, naturally imbedded in a shaly piece of coal.
These rocks approach towards true granites in one direction, and through quartz-porphyry and felsite to rhyolite in another probably depending upon the conditions of cooling and consolidation. In their mode of weathering and general appearance on a large scale, they present a marked contrast to the basic lavas with which they are in contact from the coast of L. na Keal to that of L. Buy.
Word Of The Day