Notes on mineralogy. No. VIII. On the felspar and mica of the granite of Canton / by Samuel Haughton.

  • Samuel Haughton
Date:
[1859]
Catalogue details

Licence: Public Domain Mark

Credit: Notes on mineralogy. No. VIII. On the felspar and mica of the granite of Canton / by Samuel Haughton. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

    3/4 page 3
    The miiipralogical formulae of the fouv minerals arc :— I. Lepidomelane: top; 7K -| j-L ii)(3R0)-f ^(K^03)JSi03'. II. Black Mica of Carlow : [l^(3R0) + ^(Il^03)]si03^. III. Black Mica of Donegal: [m)(3ko)+^(R»o3)]s>o»^. IV. Black Mica of Canton : It appears to me that the preceding formula?^ representing black micas from Russia, Ireland, and China, balance around a mean or average formula, which may be regarded as the type species of this mineral; viz.— +il(^'o»]s,o». This abstract or theoretical black mica probably exists only as an idea or conception in our minds, and may not have a concrete development in any place; but it must be regarded as an essen- tial constituent of the original granite formed in the astrono- mical epoch by the cooling of our globe. All our researches tend to prove that there is an original or type-granite, charac- teristic of the azoic epoch of the earth's history, marked mine- ralogically by the presence of four important minerals,— 1. Quartz; 2. Orthoclase felspar; 3. Black mica; 4. White mica; and marked chemically by the abundance of potash and the absence of lime. Trinitv College, Dublin, M'arch 10, 1859. I
    digitised image 1
    digitised image 2
    digitised image 3