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The distribution of gold and silver in the crystalline rocks of the Malvern Hills

Published online by Cambridge University Press:  14 March 2018

A. Brammall  and
D. L. Dowie
A. Brammall
Affiliation:
Geological Department, Imperial College of Science and Technology, London
D. L. Dowie
Affiliation:
Geological Department, Imperial College of Science and Technology, London
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Extract

In re-examining the crystalline rocks of the Malvern Hills, the senior author has had occasion to apply quantitative spectroscopic data for the rarer constituents of hornblendes and micas. The recognition of silver in the spectrograms of biotite led to tentative fire-assays of granitic rocks in bulk-a procedure which revealed the presence also of gold.

The assay results for this preliminary suite of granitic types are given below; values less than 5 grains per ton are returned as 'traces':

The higher values appear to be related to the reddening of the felspars, which is a widespread 'late' pneumatolytic effect; it is conspicuous in the major granite masses and related pegmatites, but somewhat local and 'arterial' in its distribution over rocks of pre granite age. Among the igneous rocks of post-granite age, the intrusive granophyric quartz-diabase ('Ivy Scar' type) shows only feeble reddening; the newer dolerites are unaffected.

Type
Research Article
Information
Mineralogical magazine and journal of the Mineralogical Society , Volume 24 , Issue 152 , March 1936 , pp. 260 - 264
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1936

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References

Note

page 262 note 1 Smethurst, A. F., Anomalies in the analytical determination of water in epidote. Min. Mag.,1935, vol. 24, pp. 173-179.Google Scholar