Notes on mineralogy. No. VII. On some rocks and minerals from central India : including two new species, hislopite and hunterite / by Samuel Haughton.

  • Haughton, Samuel.
Date:
[1859]
Catalogue details

Licence: Public Domain Mark

Credit: Notes on mineralogy. No. VII. On some rocks and minerals from central India : including two new species, hislopite and hunterite / 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.

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    time of its eruption (or deposition?). If so formed, it should not be considered as a decomposed mineral at all, but as an independent hydrated silicate of alumina, formed under great pressure and at a high temperature, water being present. In the granites of Leinster, the margarodite mica, which is present in large quantities, contains .5 or 6 per cent, of water; and yet it has never been, nor could it properly be, looked upon as the result of any metamorphic action on the rock. I believe the hydrated aluminous silicate of Nagpur to have been formed in the granite originally, or at least that, if it be the result of subsequent metamorphic action, the latter must have taken place at a high heat, and, as water was present, under a great pressure. If the destruction of orthoclase was necessary to its formation, as fast as the silicate of potash was removed by the heated water (probably red-hot), the silica must have been replaced, perhaps at the expense of the quartz of the granite, which is veiy abundant; or, which comes to the same, the me- tamorphosing agent was highly heated water under pressure, holding silica in solution, as we know it to be capable of doing to a very great extent. In whatever point of view we regard this mineral, it must be considered one of great interest, in consequence of its being a hydrated aluminous silicate, without protoxide bases, and con- taining a proportion of silica to alumina the same as that found in orthoclase. I am of opinion that it is a new mineral species, and I would propose to call it Hunterite, in honour of one of the gentlemen who brought it to England. If we neglect the lime and magnesia, it may be regarded as having the following mi- neralogical formula,— 5[A1^03, 3Si03 + 3HO] + [HO, 3Si03]; . . (II.) being, in fact, composed of five atoms of a hydrated tersilicate of alumina* combined with one atom of a hyaline silica of admitted composition. It appears to me to be a confirmation of this view of the mineral, that in the gneiss that accompanies the granite of Nagpur, and is often undistinguishable from it, this fatty fel- spar often passes into yellow and pinkish opalescent minerals, with which it evidently has the closest relation. If we take account of all the elements present, and adopt Scheerer^s view of the replacement of magnesia by three atoms of water, we find the following, which is exact:— 403[AFO^ 3Si03+HO]+256[32q|si03] +215HO; or, approximately, 4[2(AP03,3Si03) + 3HO]+5[3j^Q|si03]. . (III.) * In fact, an aluminous Glauconite.