Charnockite, St. Thomas Mount - AbsoluteAstronomy.com

Charnockite, St. Thomas Mount, located to the south of the Chennai

Chennai

Chennai , formerly known as Madras or Madarasapatinam , is the capital city of the Indian state of Tamil Nadu, located on the Coromandel Coast off the Bay of Bengal. Chennai is the fourth most populous metropolitan area and the sixth most populous city in India...

city, in Pallavaram

Pallavaram

Pallavapuram Municipality was constituted as a III Grade Municipality on 17.01.1970 vide G.o.No. 55 R.D. & L.A. Department dated 12.01.1970, by Combining the following Town Panchayats and Panchayats.* Zamin Pallavaram Town Panchayat* Issa Pallavaram Town Panchayat...

suburb, Tamil Nadu

Tamil Nadu

Tamil Nadu is one of the 28 states of India. Its capital and largest city is Chennai. Tamil Nadu lies in the southernmost part of the Indian Peninsula and is bordered by the union territory of Pondicherry, and the states of Kerala, Karnataka, and Andhra Pradesh...

, is a characteristically profuse exposure of quartz

Quartz

Quartz is the second-most-abundant mineral in the Earth's continental crust, after feldspar. It is made up of a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall formula SiO2. There are many different varieties of quartz,...

–feldspar

Feldspar

Feldspars are a group of rock-forming tectosilicate minerals which make up as much as 60% of the Earth's crust....

–hypersthene

Hypersthene

Hypersthene is a common rock-forming inosilicate mineral belonging to the group of orthorhombic pyroxenes. Many references have formally abandoned this term, preferring to categorise this mineral as enstatite or ferrosilite. It is found in igneous and some metamorphic rocks as well as in stony and...

rock, illustrated by occurrence of two pyroxene

Pyroxene

The pyroxenes are a group of important rock-forming inosilicate minerals found in many igneous and metamorphic rocks. They share a common structure consisting of single chains of silica tetrahedra and they crystallize in the monoclinic and orthorhombic systems...

facies

Facies

In geology, facies are a body of rock with specified characteristics. Ideally, a facies is a distinctive rock unit that forms under certain conditions of sedimentation, reflecting a particular process or environment....

metamorphism

Metamorphism

Metamorphism is the solid-state recrystallization of pre-existing rocks due to changes in physical and chemical conditions, primarily heat, pressure, and the introduction of chemically active fluids. Mineralogical, chemical and crystallographic changes can occur during this process...

.

The name "Charnockite, St. Thomas Mount" originated from the use of the rocks quarried from a central band in the St.Thomas Mount as tombstone of Job Charnock, the founder of Kolkata

Kolkata

Kolkata , formerly known as Calcutta, is the capital of the Indian state of West Bengal. Located on the east bank of the Hooghly River, it was the commercial capital of East India...

in 1679. Several incidents in Charnock’s life are linked to Charnockite

Charnockite

Charnockite is applied to any orthopyroxene-bearing granite, composed mainly of quartz, perthite or antiperthite and orthopyroxene , as an end-member of the charnockite series.-Charnockite series:...

rock, Chennai city (formerly Madras) and the St. Thomas Mount.

Geography and topography

Charnockite rock series is an ancient formation, similar to granite

Granite

Granite is a common and widely occurring type of intrusive, felsic, igneous rock. Granite usually has a medium- to coarse-grained texture. Occasionally some individual crystals are larger than the groundmass, in which case the texture is known as porphyritic. A granitic rock with a porphyritic...

, which has intruded into igneous rocks. It is found not only in St. Thomas Mount but also extends south of the Chingleput

Chingleput

Chingleput or Chengalpattu or Chengalpet is a city and a municipality in Kanchipuram district in the state of Tamil Nadu, India. The name of the city is derived from the old nomenclature 'chenkazhuneer patru'...

in Tamil Nadu. It is also traced to the Nilgiri hills with southern trend extending to the Malabar district

Malabar District

Malabar District was an administrative district of Madras Presidency in British India and independent India's Madras State. The British district included the present-day districts of Kannur, Kozhikode, Wayanad, Malappuram, Palakkad , and Chavakad Taluk of Thrissur District in the northern part of...

, and former feudal states of Cochin and Travancore

Travancore

Kingdom of Travancore was a former Hindu feudal kingdom and Indian Princely State with its capital at Padmanabhapuram or Trivandrum ruled by the Travancore Royal Family. The Kingdom of Travancore comprised most of modern day southern Kerala, Kanyakumari district, and the southernmost parts of...

, princely towns in Kerala

Kerala

or Keralam is an Indian state located on the Malabar coast of south-west India. It was created on 1 November 1956 by the States Reorganisation Act by combining various Malayalam speaking regions....

. It rises further above the sea level

Sea level

Mean sea level is a measure of the average height of the ocean's surface ; used as a standard in reckoning land elevation...

to form the great mass of Srilanka (Ceylon). The massive formations are more in the form of plateau

Plateau

In geology and earth science, a plateau , also called a high plain or tableland, is an area of highland, usually consisting of relatively flat terrain. A highly eroded plateau is called a dissected plateau...

(some of them at elevations between 6000 ft (1,828.8 m) and 7000 ft (2,133.6 m) that facilitates formation of lakes.

History

One of the earliest memorials in Chennai is the peaceful little Portuguese

Portuguese people

The Portuguese are a nation and ethnic group native to the country of Portugal, in the west of the Iberian peninsula of south-west Europe. Their language is Portuguese, and Roman Catholicism is the predominant religion....

chapel on top of the hill (a flight of 132 steps leads to the summit) and built at the site where Doubting Thomas

Doubting Thomas

A Doubting Thomas is someone who will refuse to believe something without direct, physical, personal evidence; a skeptic.-Origin:The term is based on the Biblical account of Thomas the Apostle, a disciple of Jesus who doubted Jesus' resurrection and demanded to feel Jesus' wounds before being...

, the Apostle

Apostle (Christian)

The term apostle is derived from Classical Greek ἀπόστολος , meaning one who is sent away, from στέλλω + από . The literal meaning in English is therefore an "emissary", from the Latin mitto + ex...

of India, was martyred in 72 A.D. and thereafter the hill has been famously known as the St. Thomas Mount

St. Thomas Mount

St. Thomas Mount, or Parangimalai is a small hillock located in Chennai, Tamil Nadu, India. Located near the neighbourhood of Guindy and very close to Chennai International Airport, St. Thomas Mount is associated with St. Thomas, the apostle of Christ, who is believed to have been martyred here...

.

The earliest recorded history related to the Charnockite is of an announcement made in 1892 by Thomas Oldham of the Geological Survey of India

Geological Survey of India

Geological Survey of India , established in 1851 is a government organization in India which is an attached office to the Ministry of Mines of Union Government of India for conducting geological surveys and studies. It is one of the oldest of such organizations in the world and the second oldest...

, of the occurrence of hypersthene granite in South India

South India

South India is the area encompassing India's states of Andhra Pradesh, Karnataka, Kerala and Tamil Nadu as well as the union territories of Lakshadweep and Pondicherry, occupying 19.31% of India's area...

. In 1893, Dr T.H.Holland, the then Chief of the Geological Survey of India reported that the Hypderstehene granites found in Madras (Chennai) was associated with large masses of norite

Norite

Norite is a mafic intrusive igneous rock composed largely of the calcium-rich plagioclase labradorite and hypersthene with olivine. Norite is essentially indistinguishable from gabbro without thin section study under the petrographic microscope...

. It was also noted that the same type of stone was used for the tombstone of Job Charnock and that it was extracted from the neighbourhood of St Thomas Mount.
Following the above finding, in 1893, Holland, had read a paper at the Asiatic Society of Bengal titled “The Petrology

Petrology

Petrology is the branch of geology that studies rocks, and the conditions in which rocks form....

of Job Charnock's Tombstone” and suggested that the rock which was of a new type be named as the ‘Charnockite rock’ in honour of the founder of Calcutta who had become the unaware means of bringing this rock to Calcutta. Thus, 200 years after his death the rock from Pallavaram (suburb of Chennai) was named Charnockite.

Recent studies in 1950 by Pascoe suggest that the material used in Charnock’s tombstone was quarried from a central band in the St. Thomas Mount.

In 1975, the Geological Survey of India

Geological Survey of India

declared the monument "Charnockite, St. Thomas Mount" in memory of Job Charnock for whom the stone from this hill, (which was then called the Pallavaram Gneiss

Gneiss

Gneiss is a common and widely distributed type of rock formed by high-grade regional metamorphic processes from pre-existing formations that were originally either igneous or sedimentary rocks.-Etymology:...

) was shipped to Calcutta for building his tomb

Tomb

A tomb is a repository for the remains of the dead. It is generally any structurally enclosed interment space or burial chamber, of varying sizes...

. Since then “Charnockite” is also prefixed with the famous “St. Thomas Mount”.

Job Charnock, a servant and administrator of the English East India Company, is credited for founding the city of Calcutta in 1686, 50 years after the city of Madras was founded.

Several incidents of Charnock’s association with Madras and the St. Thomas Mount have been cited. In 1655, he arrived in Madras and proceeded to Bengal

Bengal

Bengal is a historical and geographical region in the northeast region of the Indian Subcontinent at the apex of the Bay of Bengal. Today, it is mainly divided between the sovereign land of People's Republic of Bangladesh and the Indian state of West Bengal, although some regions of the previous...

where he was to serve in Cossim Bazar. Subsequently he went to Patna

Patna

Paṭnā , is the capital of the Indian state of Bihar and the second largest city in Eastern India . Patna is one of the oldest continuously inhabited places in the world...

(1657), in Bihar

Bihar

Bihar is a state in eastern India. It is the 12th largest state in terms of geographical size at and 3rd largest by population. Almost 58% of Biharis are below the age of 25, which is the highest proportion in India....

and in 1686 he became the Agent of the Company. He fled to Madras in 1689 as he was thrown out by the local Muslim

Muslim

A Muslim, also spelled Moslem, is an adherent of Islam, a monotheistic, Abrahamic religion based on the Quran, which Muslims consider the verbatim word of God as revealed to prophet Muhammad. "Muslim" is the Arabic term for "submitter" .Muslims believe that God is one and incomparable...

rulers during the Anglo–Moghal war. He was given protection by Governor Elihu Yale at Madras for 18 months and who also supported him fully to return to Bengal

Bengal

. This subsequently resulted in establishing Kolkatta in 1690 by Job Charnock. He rescued an Indian women from Bihar

Bihar

, who was about to commit Sati

Sati (practice)

For other uses, see Sati .Satī was a religious funeral practice among some Indian communities in which a recently widowed woman either voluntarily or by use of force and coercion would have immolated herself on her husband’s funeral pyre...

on the funeral

Funeral

A funeral is a ceremony for celebrating, sanctifying, or remembering the life of a person who has died. Funerary customs comprise the complex of beliefs and practices used by a culture to remember the dead, from interment itself, to various monuments, prayers, and rituals undertaken in their honor...

pyre

Pyre

A pyre , also known as a funeral pyre, is a structure, usually made of wood, for burning a body as part of a funeral rite...

of her husband, by gallantly blazing with guns, and later married her and renamed her as Maria. They had one son (who predeceased them) and three daughters –Mary, Elizabeth and Catherine – who married men of the reputed John Company Establishment in Bengal –. They were baptized on 19 August 1689 in front the Baptismal Font (picture of the Font and the plaque in the gallery testifies the dates) of black Pallavaram granite that existed on the Mount since 1680 (but shifted to the St Mary's Church

St. Mary's Church (Fort St. George)

St. Mary's Church located at Fort St George, is the oldest Anglican church East of Suez and also the oldest British building in India. The church is popularly known as the 'Westminster Abbey of the East'.- History :...

at Fort St. George in 1885).

Geology

The constituents of the rock suggests of its origin in particularly dry and high temperature conditions which is deduced to have an important bearing in explicating prehistoric crustal development of the earth.
From the time Holland, named the rock as Charnockite, its characteristics have been extensively studied by several researches in Earth Science

Earth science

Earth science is an all-embracing term for the sciences related to the planet Earth. It is arguably a special case in planetary science, the Earth being the only known life-bearing planet. There are both reductionist and holistic approaches to Earth sciences...

s over the century

Century

A century is one hundred consecutive years. Centuries are numbered ordinally in English and many other languages .-Start and end in the Gregorian Calendar:...

. An analysis of three charnockites in the region, extending from St. Thomas Mount – Pallavaram

Pallavaram

–Tambaram

Tambaram

Tambaram is a suburb of Chennai situated 27 km south of the city in Tamil Nadu, India. It is an urban node. Tambaram is a hub to all major destinations in south Tamil Nadu as it lies on the busy Chennai–Trichy national highway. The highway and the railway line from Chennai Egmore to...

, south of the city of Chennai, carried out on the compositional characteristics of coexisting orthopyroxene, garnet

Garnet

The garnet group includes a group of minerals that have been used since the Bronze Age as gemstones and abrasives. The name "garnet" may come from either the Middle English word gernet meaning 'dark red', or the Latin granatus , possibly a reference to the Punica granatum , a plant with red seeds...

and biotite

Biotite

Biotite is a common phyllosilicate mineral within the mica group, with the approximate chemical formula . More generally, it refers to the dark mica series, primarily a solid-solution series between the iron-endmember annite, and the magnesium-endmember phlogopite; more aluminous endmembers...

has established several petrographic varieties within the charnockites–enderbite

Enderbite

In geology, enderbite is primarily an igneous rock of the charnockite series, consisting essentially of quartz, antiperthite , orthopyroxene and magnetite, and is equivalent to an orthopyroxene bearing tonalite. It is named for its occurrence in Enderby Land, Antarctica.-References:Classification...

s such as the granulite

Granulite

Granulites are medium to coarse–grained metamorphic rocks that have experienced high temperature metamorphism, composed mainly of feldspars sometimes associated with quartz and anhydrous ferromagnesian minerals, with granoblastic texture and gneissose to massive structure...

s and gneisses corresponding to adamellite, monzonite

Monzonite

Monzonite is an intermediate igneous intrusive rock composed of approximately equal amounts of sodic to intermediate plagioclase and orthoclase feldspars with minor amounts of hornblende, biotite and other minerals...

, granite and others.
Another study on the general characteristics of the rocks of this series has recorded that the rocks are in general bluish gray or darkish in colour and extremely fresh in appearance with an even grained granular structure. The mineral composition shows an unvarying presence of pleochroic rhombic pyroxene

Pyroxene

. The other femic minerals noted are augite

Augite

Augite is a single chain inosilicate mineral, 2O6. The crystals are monoclinic and prismatic. Augite has two prominent cleavages, meeting at angles near 90 degrees.-Characteristics:Augite is a solid solution in the pyroxene group...

and hornblende

Hornblende

Hornblende is a complex inosilicate series of minerals .It is not a recognized mineral in its own right, but the name is used as a general or field term, to refer to a dark amphibole....

with minute grains of opaque iron ores and these minerals have been noted to cluster together. Flagioclase feldspars, alkali

Alkali

In chemistry, an alkali is a basic, ionic salt of an alkali metal or alkaline earth metal element. Some authors also define an alkali as a base that dissolves in water. A solution of a soluble base has a pH greater than 7. The adjective alkaline is commonly used in English as a synonym for base,...

feldspars and quartz are the salic minerals present in this series of rocks.

In order to determine the geological age of the charnockitic region of the Pallavaram area in the Madras (Chennai) Block, palaeomagnetic investigations were carried out at 12 sites, which suggested an age of magnetization in the Pallavaram charnockites as 2600 Ma while in the St. Thomas Mount the period of emplacement was assessed as 1650 Ma (Mesoproterozoic

Mesoproterozoic

The Mesoproterozoic Era is a geologic era that occurred between 1600 Ma and 1000 Ma . The Mesoproterozoic was the first period of Earth's history with a respectable geological record. Continents existed in the Paleoproterozoic, but we know little about them...

). There was a further inference that the Madras block granulites indicated crust

Crust (geology)

In geology, the crust is the outermost solid shell of a rocky planet or natural satellite, which is chemically distinct from the underlying mantle...

al evolution similar to those in the Eastern Ghats

Eastern Ghats

The Eastern Ghats or Eastern Ghauts are a discontinuous range of mountains along India's eastern coast. The Eastern Ghats run from West Bengal state in the north, through Orissa and Andhra Pradesh to Tamil Nadu in the south passing some parts of Karnataka. They are eroded and cut through by the...

belt with identical palaeopoles from both the areas. The study also noted that “pressure, temperature and the chemical potential of water were constant for assemblages separated by large distances.”

Trivia

An interesting Oscar Wilde

Oscar Wilde

Oscar Fingal O'Flahertie Wills Wilde was an Irish writer and poet. After writing in different forms throughout the 1880s, he became one of London's most popular playwrights in the early 1890s...

memorial monument erected in the year 2000 on the centenary of his death, seen in Merrion Square

Merrion Square

Merrion Square is a Georgian square on the southside of Dublin city centre. It was laid out after 1762 and was largely complete by the beginning of the 19th century. It is considered one of the city's finest surviving squares...

, Dublin, Ireland

Ireland

Ireland is an island to the northwest of continental Europe. It is the third-largest island in Europe and the twentieth-largest island on Earth...

opposite to his childhood house, is reclining on a 35 ton boulder of quartz from the Wicklow Mountains

Wicklow Mountains

The Wicklow Mountains form the largest continuous upland area in Ireland. They occupy the whole centre of County Wicklow and stretch outside its borders into Counties Carlow, Wexford and Dublin. Where the mountains extend into County Dublin, they are known locally as the Dublin Mountains...

, Ireland

Ireland

Ireland is an island to the northwest of continental Europe. It is the third-largest island in Europe and the twentieth-largest island on Earth...

. The statue (pictured) is splendidly sculpted out of semi–precious stones with blue

Blue

Blue is a colour, the perception of which is evoked by light having a spectrum dominated by energy with a wavelength of roughly 440–490 nm. It is considered one of the additive primary colours. On the HSV Colour Wheel, the complement of blue is yellow; that is, a colour corresponding to an equal...

pearl

Pearl

A pearl is a hard object produced within the soft tissue of a living shelled mollusk. Just like the shell of a mollusk, a pearl is made up of calcium carbonate in minute crystalline form, which has been deposited in concentric layers. The ideal pearl is perfectly round and smooth, but many other...

granite trousers (Larvikite

Larvikite

Larvikite is a variety of monzonite, notable for the presence of handsome, thumbnail-sized crystals of feldspar. These feldspars are known as ternary because they contain significant components of all three end-member feldspars...

known as blue granite from the western shores of Oslo Fjord in Norway

Norway

Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...

, jacket

Jacket

A jacket is a hip- or waist-length garment for the upper body. A jacket typically has sleeves, and fastens in the front. A jacket is generally lighter, tighter-fitting, and less insulating than a coat, which is outerwear...

of Nephrite

Nephrite

Nephrite is a variety of the calcium and magnesium-rich amphibole mineral actinolite . The chemical formula for nephrite is Ca25Si8O222. It is one of two different mineral species called jade. The other mineral species known as jade is jadeite, which is a variety of pyroxene...

jade

Jade

Jade is an ornamental stone.The term jade is applied to two different metamorphic rocks that are made up of different silicate minerals:...

[originally a 980 kilograms (2,160.5 lb) block from the Yukon

Yukon

Yukon is the westernmost and smallest of Canada's three federal territories. It was named after the Yukon River. The word Yukon means "Great River" in Gwich’in....

], Canada

Canada

Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

, the red cuff

Cuff

A cuff is an extra layer of fabric at the lower edge of the sleeve of a garment covering the arms. In US usage the word may also refer to the end of the leg of a pair of trousers...

s and collar

Collar (clothing)

In clothing, a collar is the part of a shirt, dress, coat or blouse that fastens around or frames the neck. Among clothing construction professionals, a collar is differentiated from other necklines such as revers and lapels, by being made from a separate piece of fabric, rather than a folded or...

made of Thulite

Thulite

Thulite is an opaque, massive pink manganese-bearing variety of the mineral zoisite. Manganese substitutes for calcium in the structure with up to two percent Mn2+. Thulite is often mottled with white calcite and occurs as veins and fracture fillings transecting many types of rock...

from Norway

Norway

, shoes and socks

SOCKS

SOCKS is an Internet protocol that routes network packets between a client and server through a proxy server. SOCKS5 additionally provides authentication so only authorized users may access a server...

made of black charnockite granite

Granite

from India

India

India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...

and holding a green

Green

Green is a color, the perception of which is evoked by light having a spectrum dominated by energy with a wavelength of roughly 520–570 nanometres. In the subtractive color system, it is not a primary color, but is created out of a mixture of yellow and blue, or yellow and cyan; it is considered...

carnation

Carnation

Dianthus caryophyllus is a species of Dianthus. It is probably native to the Mediterranean region but its exact range is unknown due to extensive cultivation for the last 2,000 years. It is the wild ancestor of the garden carnation.It is a herbaceous perennial plant growing to 80 cm tall...

to his breast.

Access

The charnockite rocks at St. Thomas Mount (about 60 m (196.9 ft) high above ground) is located in the southern part of Chennai city. Chennai, as the capital of Tamil Nadu, is very well connected by road

Road

A road is a thoroughfare, route, or way on land between two places, which typically has been paved or otherwise improved to allow travel by some conveyance, including a horse, cart, or motor vehicle. Roads consist of one, or sometimes two, roadways each with one or more lanes and also any...

, rail

Rail transport

Rail transport is a means of conveyance of passengers and goods by way of wheeled vehicles running on rail tracks. In contrast to road transport, where vehicles merely run on a prepared surface, rail vehicles are also directionally guided by the tracks they run on...

, sea

Sea

A sea generally refers to a large body of salt water, but the term is used in other contexts as well. Most commonly, it means a large expanse of saline water connected with an ocean, and is commonly used as a synonym for ocean...

and air with rest of the country and the world. The Chennai International Airport is 3 km (1.9 mi) away from the Mount. Within the city, it is in the neighborhood of Guindy

Guindy

Guindy is one of the important neighbourhoods of Chennai , Tamil Nadu, India. It is located in the South-Western part of the city. It is the entry point or the gateway to Chennai city from the Southern parts of Tamil Nadu and the South Western suburbs of Chennai...

, 9.7 mi (15.6 km) from Fort St. George, 4 mi (6.4 km) from South west of Santhome-de-Meliyapore (burial ground of St. Thomas), and close to the flying range. Chennai Suburban Railway South line has a railway station at St. Thomas, 18 km (11.2 mi) from starting point.

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