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Ægirine and Riebeckite Anorthoclase Rocks Related to the “Grorudite-Tinguaite” series, from the neighbourhood of Adowa and Axum, Abyssinia

Published online by Cambridge University Press:  14 March 2018

G. T. Prior
G. T. Prior*
Affiliation:
Mineral Department of the British Museum
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Extract

In 1869 the late Dr. Sadebeek gave a brief description of a collection of rocks, accompanied by a map and profiles, made by Dr. W. Sehimper in the neighbourhood of Adowa and Axum, Abyssinia.

In the British Museum is a very similar collection, which was purchased from Dr. Schimper about the same time. As some of these rocks showed points of resemblance to the riebeckite-trachytes of Senafé, recently described by the author, a somewhat more detaBed petrographical examination of the specimens than Dr. Sadebeck was able to afford them appeared to promise something of interest.

Type
Research Article
Information
Mineralogical magazine and journal of the Mineralogical Society , Volume 12 , Issue 57 , July 1900 , pp. 255 - 273
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1900

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References

page 255 note 1 Zeits. Ges. f. Erdkunde, IV, 1869, pp. 347-52.

page 255 note 2 Min. Mag. 1899, XII, 92.

page 255 note 3 Brögger, Eruptivgesteine des Kristianiagebietes, I.

page 261 note 1 The "segirine-granite" from Miask, described by Pirsson (Am. J. Sci. IX, 1900, p. 199), though of coarser grain, is a closely related rock.

page 262 note 1 This extinction in sectors is precisely similar to that observed by Grgnzer in the orthoclase-like mineral occurring in druses in leucite-tephrite from the Eulenberg (Min Mith. XI, 1889-90, p. 277, Tar V, figs. 4 and 5). A redetermination of the alkalies in this minerat would be desirable. It may possibly be anorthoclase.

page 262 note 2 Brögger, Eruptivgesteine des Kristianiagebietes, I, p. 48.

page 265 note 1 Brögger remarks in connection with grorudite and sölvsbergite that it is probable that the short rectangular foxm of the felspars of the groundmass is connected with more acid composition, and the long lath.shaped form with a less amount of silica. (l. c. p. 48.)

page 265 note 2 The ægirine-riebeekite-auorthoclase rock from Akub Teriki, Senafé, described by the author in a previous paper (Min. Mag. XII, 95) should without doubt be also referred to the sölvsbergites.

page 271 note 1 Bragger's cataphorite was not observed in these Abyssinian rocks.

page 272 note 1 Beitr. Geol. Kennt d. Ost. Afrika, 74 and 81, 1891.

page 273 note 1 Lacroix (Comptes Rendus, CXXVIII, 1467) has recently described rhyolites from Somali-land containing ægirine and riebeekite.