Dyer, Alan; Green, David I.; Tindle, Andrew G. and Williams, Craig D.
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Quantitative chemical analyses of a number of millimetre-sized crystals detached from specimens labelled 'heulandite' from Wheal Hazard, St Just, Cornwall show that most of their compositions lie within the closely related clinoptilolite series of minerals: specifically, potassium- and magnesium-rich clinoptilolite-Ca. An average of 28 analyses produces the chemical formula: (Ca1.87,Ku1.31,Mg0.86,Na0.12,Sr0.07,Ba0.04,)[AI7.22Si28.81O72].nH20. The crystals occur in fine grained metasedimentary rocks of the Mylor Slate Formation, in fractures that post-date the development of the metamorphic fabric. It seems likely that the crystals developed as a result of hydrothermal alteration of the rock during the final stages of the cooling of the Land's End Granite. On the basis of our analyses it is unsafe to label specimens from the well-known 'heulandite' locality at Wheal Hazard as heulandite.
|Item Type:||Journal Article|
|Copyright Holders:||2006 The Authors, 2006 The Russell Society|
|Interdisciplinary Research Centre:||Centre for Earth, Planetary, Space and Astronomical Research (CEPSAR)|
|Depositing User:||Elizabeth Lomas|
|Date Deposited:||04 Mar 2009 16:32|
|Last Modified:||19 Sep 2012 12:13|
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