Charnockite is a series of foliated metamorphosed igneous rocks of wide distribution and great importance in India, Ceylon, Madagascar and Africa. Volcanic rock on North America Plutonic rock on North America Igneous rocks are formed when molten rock (magma) cools and solidifies, with or without crystallization, either below the surface as intrusive (plutonic) rocks or on the surface as extrusive (volcanic) rocks. ... A satellite composite image of Africa Africa is the worlds second-largest continent in both area and population, after Asia. ...

The name was given by Dr T. H. Holland from the fact that the tombstone of Job Charnock, the founder of Calcutta, is made of a block of this rock. The charnockite series includes rocks of many different types, some being acid and rich in quartz and microcline, others basic and full of pyroxene and olivine, while there are also intermediate varieties corresponding mineralogically to norites, quartz-norites and diorites. A special feature, recurring in many members of the group, is the presence of strongly pleochroic, reddish or green hypersthene. This article is on Calcutta/Kolkata, the city. ... Quartz is the second most abundant mineral in the Earths crust. ... Feldspar (from the German Feld, field, and Spat, a rock that does not contain ore) is the name of an important group of rock-forming minerals which make up perhaps as much as 60% of the Earths crust. ... The Pyroxenes are a group of important rock-forming silicate minerals found in many igneous and metamorphic rocks. ... Olivine The mineral olivine is a magnesium iron silicate with the formula (Mg,Fe)2SiO4 in which the ratio of magnesium and iron varies between the two endmembers of the series: forsterite (Mg-rich) and fayalite (Fe-rich). ... Categories: Mineral stubs | Igneous rocks ... Hypersthene is a common rock-forming mineral belonging to the group of orthorhombic pyroxenes. ...

Many of the minerals of these rocks are schillerized, as they contain minute platy or rod-shaped enclosures, disposed parallel to certain crystallographic planes or axes. The reflection of light from the surfaces of these enclosures gives the minerals often a peculiar appearance, e.g. the quartz is blue and opalescent, the feldspar has a milky shimmer like moonshine, the hypersthene has a bronzy metalloidal gleam. Very often the different rock types occur in close association as one set forms bands alternating with another set,or veins traversing it, and where one facies appears the others also usually are found. Feldspar (from the German Feld, field, and Spat, a rock that does not contain ore) is the name of an important group of rock-forming minerals which make up perhaps as much as 60% of the Earths crust. ...

The term charnockite consequently is not the name of a rock, but of an assemblage of rock types, connected in their origin because arising by differentiation of the same parent magma. The banded structure which these rocks commonly present in the field is only in a small measure due to crushing, but is to a large extent original, and has been produced by fluxion in a viscous crystallizing intrusive magma, together with differentiation or segregation of the mass into bands of different chemical and mineralogical composition. There have also been, of course, earth movements acting on the solid rock at a later time and injection of dikes both parallel to and across the primary foliation. In fact, the history of the structures of the charnockite series is the history of the most primitive gneisses in all parts of the world, for which we cannot pretend to have as yet any thoroughly satisfactory explanations to offer. This article is about the type of molten rock. ... Banded gneiss with dike of granite orthogneiss Gneiss is a common and widely distributed type of rock formed by high grade regional metamorphic processes from preexisting formations that were originally either igneous or sedimentary rocks. ...

A striking fact is the very wide distribution of rocks of this group in the southern hemisphere; but they also, or rocks very similar to them, occur in Norway, France, Germany, Scotland and North America, though in these countries they have been mostly described as pyroxene granulites, pyroxene gneisses, anorthosites, &c. They are usually regarded as being of Archean age (preCambrian), and in most cases this can be definitely proved, though not in all. It is astonishing to find that in spite of their great age their minerals are often in excellent preservation.

In India they form the Nilgiri Hills, the Shevaroys and part of the Western Ghats, extending southward to Cape Comorin and reappearing in Ceylon. Although they are certainly for the most part igneous gneisses (or orthogneisses), rocks occur along with them, such as marbles, scapolite limestones, and corundum rocks, which were probably of sedimentary origin. Map of The Nilgiris district The Nilgiris or Blue Mountains are a range of mountains and a district in the south-Indian states of Tamil Nadu and Kerala. ... Shavaroys is the anglicised name for the Servarayan range of hills rising above the town of Salem in Tamilnadu, India. ... The Western Ghats or Sahyadri mountains run along the western edge of Indias Deccan Plateau, and separate the plateau from a narrow coastal plain along the Arabian Sea. ... Kanyakumari is a town and a cape at the southernmost tip of the Indian peninsula. ...

This article incorporates text from the public domain 1911 Encyclopædia Britannica. The public domain comprises the body of all creative works and other knowledge—writing, artwork, music, science, inventions, and others—in which no person or organization has any proprietary interest. ... The Eleventh Edition of the Encyclopædia Britannica (1911) in many ways represents the sum of knowledge at the beginning of the 20th century. ...