MINERALOGICAL MAGAZINE JOURI~AL OF THE MINERALOGICAL SOCIETY
Summary. Reyerite is found in close association with gyrolite in the nletamorphic aureole of the volcanic plug of 'S Airde Beinn, northern Mull, and has apparently been formed by metamorphism of the gyrolite. The gyrolite, with a composition close to Cal~Si~40~0(OH)s.14H20, closely approaches t...
| Main Authors: | , , , |
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| Format: | Text |
| Language: | English |
| Published: |
1965
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| Subjects: | |
| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.625.7699 http://www.minersoc.org/pages/Archive-MM/Volume_35/35-269-1.pdf |
| Summary: | Summary. Reyerite is found in close association with gyrolite in the nletamorphic aureole of the volcanic plug of 'S Airde Beinn, northern Mull, and has apparently been formed by metamorphism of the gyrolite. The gyrolite, with a composition close to Cal~Si~40~0(OH)s.14H20, closely approaches trigonal symmetry with a 9-76:t:0.02- ~ and c 3 x 22.26 • 0-1/k; biaxial with a small 2V and a 1.537, fl 1-547,? 1.549. The reyerite is trigonal with a 9.76!0.02/~, c 19.10-[_0.04/ ~ and space group p3; ~o 1.568 and ~ 1.563, and the unit cell contains about 14 atoms of Ca, 24 of Si (with some substitution by 4(Oil)-), and 14H~O as (OH)- and H~O. YROLITE and reyerite have been found closely associated in plateau basalts near the volcanic plug that forms the hill of 'S Airde Beinn, 3 miles west of Tobermory, Isle of Mull, Scotland. The gyrolite fills amygdales in the basalts just outside the aureole of the plug at the north end of the hill, and is seen as radiating aggregates of colourless plates of high birefringence associated with analcime, thomsonite, and natrolite. The reyerite is found a few yards away just within the metamorphic aureole of the plug. I t forms coarse pale-green radiating aggregates of plates of low birefringence filling amygdales and associated with the same zeolites as the gyrolite. The field relations indicate that it has been formed by mild metamorphism of the gyrolite, and it seems probable that this is also the origin of the reyerite of the type locality, at Niakornak in Greenland, where it is found in amygdales in blocks in a tuff pipe (Cornu, 1906; Boggild, 1908). This origin is compatible with the experimental work of Roy and Harker (1962), although Meyer and Jaunarajs (1961) consider that such a relationship is not possible. At higher grades of metamorphism, wollastonite has replaced the reyerite; xonolite, which the experimental work shows to be formed intermediate between reyerite and wollastonite, was not found. Gyrolite. The gyrolite is optically negative with a small 2V: refractive indices ... |
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