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Abstract

From Baron von Groddeck, chief mining councillor of
the Hartz mining districts, and director of the
Royal Prussian academy of mines at Clausthal,
Germany.
(Translated by Edgar Wolfhagen, M.B., Hobart, from the
Special Imprint of the "Magazine of the Geological
Society," 1886.)
Attention was again drawn to the collection
of specimens of minerals from Mount Bischoff, Tasmania, in
the possession of the Royal Academy for Mineralogy in
Clausthal. This collection has previously afforded me an
opportunity for making a communication about a porphyritic
topaz rock and about a peculiar topaz tourmaline deposit in
the Tasmanian tin district.
It appears, therefore, as if in the tin district of Tasmania
(as in the Schueckenstein in the south-west of Saxony) a
transformation of the rocks with topaz had taken place
during the formation of the tin deposits. This is a previously
unknown geological process of the highest interest,
since it introduces new views as to the origin of the tin
deposits. This process is probably not so isolated as would
at present appear. The discovery made by M. Schroeder is
the more interesting, as many pseudo-morphoses from topaz
to other minerals are known, but no change of another
mineral into topaz. On the Schueckenstein the transformation with topaz
occurs, according to M. Schroeder, by the topaz replacing
both tourmaline and feldspar. Minute crystals of topaz protrude into the clear
quartz in the form of needles, fibres, and bundles of fibres, or
even lie, apparently isolated, in among the quartz. The topaz is to be distinguishd from the quartz by ordinary light, by its dull colouration, and very finely granular or radiating fibrillar structure.
It remains undecided, therefore, whether the Tasmanian
tourmaline-quarzit slate has undergone a transformation into
topaz, as is the case in that of Saxony.

Item Type:	Article
Authors/Creators:	Von Groddeck, (Baron)
Keywords:	Royal Society of Tasmania, Van Diemens Land, VDL, Hobart Town, natural sciences, proceedings, records
Journal or Publication Title:	Papers and Proceedings of the Royal Society of Tasmania
ISSN:	0080-4703
Collections:	Royal Society Collection > Papers & Proceedings of the Royal Society of Tasmania
Additional Information:	In 1843 the Horticultural and Botanical Society of Van Diemen's Land was founded and became the Royal Society of Van Diemen's Land for Horticulture, Botany, and the Advancement of Science in 1844. In 1855 its name changed to Royal Society of Tasmania for Horticulture, Botany, and the Advancement of Science. In 1911 the name was shortened to Royal Society of Tasmania.
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