Borolanite
Borolanite is an historical
alkali feldspar pseudomorphs interpreted to be after leucite which occur as conspicuous white spots in the dark rock matrix.[1]
The rock occurs in the Borralan Igneous Complex or Loch Borralan Complex which is an alkalic igneous complex near Loch Borralan in northwest Scotland.[2][3]
The
igneous rocks, though some syenites, leucitophyres, and aegirine-felsites resemble borolanite in this respect. In places the nepheline syenite assumes the form of a dark rock with large rounded white spots. These last consist of an intermixture of nepheline or sodalite and alkali-feldspar. From the analogy of certain leucite syenites which are known in Arkansas, it is very probable that these spots represent original leucites which have been changed into aggregates of the above-named minerals. They resemble leucite in their shape, but have not yet been proved to have its crystalline outlines. The pseudo-leucites, as they have been called, measure one-quarter to three-quarters of an inch across. The dark matrix consists of biotite, aegirine-augite and melanite. Connected with the borolanite there are other types of nepheline syenite and pegmatite. In Finland, melanite bearing nepheline rocks have been found and described as ijolite, but the only other locality for melanite-leucite-syenite is Magnet Cove igneous complex in Arkansas.[4]
References
- ^ Parsons, I., Loch Borralan Intrusion, Volume 17: Caledonian Igneous Rocks of Great Britain Chapter 7: Late Ordovician to mid-Silurian alkaline intrusions of the North-west Highlands of Scotland, Geological Conservation Review, 2007, [1]
- ISBN 978-1862393004
- ^ Loch Borralan: Alkaline igneous intrusions
- ^ One or more of the preceding sentences incorporates text from a publication now in the public domain: Flett, John Smith (1911). "Borolanite". In Chisholm, Hugh (ed.). Encyclopædia Britannica. Vol. 4 (11th ed.). Cambridge University Press. p. 267.
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