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Some effects of artificial heating on fluorite-bearing albite-granite from St. Austell, Cornwall

By: Weymouth, J.H.
Contributor(s): Williamson, W.O.
Material type: ArticleArticleDescription: 69-80pp ; Illustration.Subject(s): Effect - Artificial heating - Fluorite bearing albite - St. Austell - Cornwall | Experimental studies - Cornwall In: Geological magazine : Vol. 94 Iss. 1-6 Year. 1957Summary: Abstract The granite consisted chiefly of albite, quartz, muscovite, microperthite, fluorite, and topaz; zircon was very rare. The low to high quartz transition enhanced thermal expansion and porosity. Heating was continued step-wise to 1,300°C. and caused an irreversible increase in porosity at all temperatures investigated. The changes undergone by the various minerals, separately or through interaction, were noted. Fluorite began to melt against muscovite or alkali-feldspar between 800° and 900°C. Muscovite developed brownish pleochroism at the lower, and was replaced by mullite at the higher, temperatures. The gradual melting of feldspar, the development of cleavages and cracks in quartz, and the invasion of these cracks by feldspathic glass resembled phenomena in certain xenoliths. The conditions that produced glass when powdered granite was heated unconfined or in a bomb are described.
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Article Article Library and Information Centre
Periodical Section
Bound Journal Collection Not for loan 002549_07
Serials/Scientific Journal Serials/Scientific Journal Library and Information Centre
Periodical Section
Bound Journal Collection 550 GEO (Browse shelf) Available 002549

Abstract
The granite consisted chiefly of albite, quartz, muscovite, microperthite, fluorite, and topaz; zircon was very rare. The low to high quartz transition enhanced thermal expansion and porosity. Heating was continued step-wise to 1,300°C. and caused an irreversible increase in porosity at all temperatures investigated. The changes undergone by the various minerals, separately or through interaction, were noted. Fluorite began to melt against muscovite or alkali-feldspar between 800° and 900°C. Muscovite developed brownish pleochroism at the lower, and was replaced by mullite at the higher, temperatures. The gradual melting of feldspar, the development of cleavages and cracks in quartz, and the invasion of these cracks by feldspathic glass resembled phenomena in certain xenoliths.

The conditions that produced glass when powdered granite was heated unconfined or in a bomb are described.

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