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IV.—On a Hornblende-Hypersthene-Peridotite from Losilwa, a low hill in Taveta District, at the S. Foot of Kilimanjaro, E. Africa

Published online by Cambridge University Press:  01 May 2009

Frederick H. Hatch
Frederick H. Hatch
Affiliation:
H. M. Geological Survey
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Extract

A Small series of rock-specimens, consisting chiefly of fragments of basalt, dolerite, volcanic conglomerate and tuff, which were collected near Kilima-njaro, by F. Holmwood, Esq., C.B., lateConsul-General at Zanzibar, was recently forwarded to the Museum at Jermyn Street, and placed by Dr. A. Geikie in my hands for determination. Among these specimens was a small block, the crystalline texture and high density of which at once arrested attention Freshly fractured surfaces of this rock present numerous glistening facets, which with the aid of the pocket-lens are seen to be the cleavagefaces of a yellowish-green, a dark-green, and a garnet-red mineral. These minerals are respectively olivine, hornblende, and hypersthene in nearly equal proportions, the hornblende being perhaps slightly predominant. They form a holocrystalline granular aggregate, in which the.grains are of nearly equal size and without crystalline contours; in other words, the structure is allotriomorphic-granular. Subordinate both in size and quantity to the three principal constituents is magnetic iron-ore.

Type
Original Articles
Information
Geological Magazine , Volume 5 , Issue 6 , June 1888 , pp. 257 - 260
Copyright
Copyright © Cambridge University Press 1888

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References

page 258 note 1 Thomson (“Through Massai-Land, ” London, 1885) repeatedly mentions the occurrence of metamorphic rocks in this neighbourhood. They are seen, according to this author, to crop out at the very foot of Kilima-njaro on the E. and S. sides. O. Mügge (Neues Jahrb. B.B. iv. 1886, p. 576) has described gneissose mica-schistsand amphibolites from the southern portion of Massai-Land, as constituting members of a “gneiss or granite-gabbro formation.”

page 259 note 1 1887, p. 260.

page 259 note 2 Sitzungsber. K. K. Akad. der Wissensch. Wien, 1866, Bd. liii. p. 260.

page 259 note 3 Sitzungsber. K. K. Akad. der Wissensch. Wien. 1867, Bd. lvi. p. 274.

page 259 note 4 Die Porphyrgesteine Oesterreichs, etc. Wien, 1S69, p. 245.

page 259 note 5 Geogn. Beschreib. des Fichtelgebirges, Gotha, 1879, p. 150.

page 260 note 1 Trans. Hoy. Soc. Edin. vol. xxix. (1880), p. 504.

page 260 note 2 Q. J. G. S. vol. xxxvii. (1881), p. 137.

page 260 note 3 Physiog. der Massig. Gest. 1887, p. 518.

page 260 note 4 Amer. Jonrn. of Sci. vol. xxxi. 1886, p. 26.

page 260 note 5 These Scourie rocks are placed by Rosenbusch among the hornblende-picrites, l.c. p. 267.