134 HOLLAND: CHARNOCKITE SERIES. 



(4) Ultra-basic forms, or pyroxenites, composed of hyper- 

 sthene, augite, hornblende, sometimes with olivine, 

 green spinel and magnetite. The hypersthenes are 

 sometimes porphyritic, but more generally are perfectly 

 granulitic. Specific gravity, 3*37 ; silica percentage, 

 47 to 50. Amphibolization of the pyroxene sometimes 

 results in an almost complete change to hornblende. 

 These four divisions are described in order below : — 



(1) Acid Division. 



Charnockite. 



In October 1892, the Director of the Geological Survey of 

 Discovery of charnock- India announced in his tri-monthly notes, the 

 lte- occurrence in South India of a rock composed 



of hypersthene, microcline, quartz and accessory iron-ores, referring 

 to it as a hypersthene-granite, 1 As at that time little more 

 was known than the mere occurrence at Pailavaram of a mass of 

 this rock, no further details were published until after my second 

 visit to Madras in September 1893. It was then found that the 

 hypersthene-granite formed large masses associated with granulitic 

 rocks, having the mineral composition of norite [infra, p. 153). At 

 about the same time the tombstone of Job Charnock, the founder 

 of Calcutta, was discovered by the Rev. H. B. Hyde in St. John's 

 Churchyard, Calcutta, and when it was found that the tombstone 

 was made of the same hypersthene-granite (which was at the time 

 thought to be a new type of rock), the name charnockite was 

 suggested for it in honour of the man who was the unconscious means 

 of bringing the first specimen of this interesting rock to the city 

 which ultimately became the capital of India. 2 



In the same year (1893) Prof. J. H. L. Vogt published the 

 first instalment of a series of papers on the " Bildung von Erzlagers- 



1 Rec. Geol. Surv. Ind. } Vol. XXV (1892), p. 190. 



* Journ. As. Soc. Beng., Vol. LXI1 (1893), p. 1G2. Job Charnock died in 1693, and the 

 tombstone was erected two years later. 



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