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Published online by Cambridge University Press: 01 May 2009
In some parts of the Alps serpentine is by no means a rare rock; indeed it is commoner than some geologists (myself included) once supposed, because much that was formerly comprehended under the term ‘serpentinous schist’ now proves to be true serpentine modified by the effects of pressure.
page 534 note 1 See Geol. Mag. Dec. II. Vol. VI. p. 362; Vol. VII. p. 538. Descriptions of some Alpine serpentines will be found in Mr. Teall's British Petrography, p. 109, et seq.
page 534 note 2 A specimen of one of the harder varieties which I have had sliced consists of a not very characteristic glaucophane (the greater part of the grains being, as has often been described, altered into a dull green hornblende), epidote, garnets (rather small), a little white mica, hematite, etc. It is difficult to offer an opinion as to the origin of these green schists. Some may be modifitd igneous rocks; others possibly altered tuffs.
page 534 note 3 According to the Swiss Geological Survey there should be some rauchwacké interstratified near the base of the quartzite, but I omit this rock as I do not hold it to be a member of the crystalline series. The quartz-schist, green-schists, and calc-mica schists belong to the great group of crystalline schists which in the Alps have such a wide distribution and occur at the top of the Crystalline (probably Arehæan) series.
page 536 note 1 A very fine specimen, on a scale about five times that figured above, was found last summer at the top of the Théodule Pass by Prof. W. Ramsay, F.R.S., and given to our Museum at University College.
page 537 note 1 The hardness of the rock is between 3 and 3·5, and its S.G. =2·67.
page 537 note 2 Possibly the mineral may be (in part at least) antigorite. Cf. the description in Teall's British Petrography, p. 113. The. larger flakes in my slides show a faint dichroism, but it is imperceptible in the smaller.
page 538 note 1 I am greatly indebted to Mr. J. Eccles, F.G.S., for verifying the opinion which I had formed, and for much additional information.
page 539 note 1 Also traces of Cr2O3 and MnO.
page 539 note 2 Q.J.G.S. vol. xxxvii. (1881) pp. 43–45.
page 539 note 3 The Fe2O3 is not indicated in the comparison, because I believe most of it is present in No. 1. as hematite. Thus it will not help us for the present purpose.
page 540 note 1 Trans. Royal Soc. Edin. vol. xxix. (1879) p. 55.Google Scholar
page 540 note 2 I am indebted to Miss C. A. Raisin for much help in this search.
page 540 note 3 Analysis of Chloritoid, Tschermak and Sipöcz, Sitz. k k. Akad. Wiss. 1879.
page 540 note 4 Analysis of ‘Sismoadine’ from Zermatt, Des Cloiseaux, Bull. Soc. Min. vol. vii. p. 80.
page 540 note 5 Loc. cit.
page 540 note 6 Curiously enough there is a similar association in Anglesey, Q.J.G.S. vol. xxxvii p. 44.Google Scholar
page 540 note 7 After microscopic examination of a specimen collected by Mr. Eccles, I think there can be little doubt the rock is an altered serpentine. The dominant mineral has all the characters of talc, but there are several grains of calcite which, by their mode of occurrence, suggest replacement (? of augite).
page 541 note 1 There are however not a few minute grains of a honey-brown, somewhat dichroic, mineral which may be a variety of hornblende.
page 541 note 2 Q.J.G.S. vol. xxxix. pp. 21–23.Google Scholar
page 541 note 3 Geol. Mag. Dec. III. Vol. IV. p. 137.