Maynes Hill quarry, Maydena district, Derwent Valley municipality, Tasmania, Australiai

Regional Level Types
Maynes Hill quarry	Quarry
Maydena district	District
Derwent Valley municipality	Municipality
Tasmania	State
Australia	Country

This quarry is in an early Cambrian pillow basalt, about 540 million years old. It is relatively weakly metamorphosed, and good basalt pillows to about a metre in size are readily visible in the quarry face. Whitish to green or grey irregular quartz/chalcedony nodules to about 20cm in diameter occur in the inter-pillow regions. These are clearly not normal vesicle-filling, like most agates in basalts, but appear to have formed from the replacement or recrystallisation of inter-pillow material (carbonates or chert?). Some of the siliceous nodules are very chalcedonic and could be termed agate, with white to dark grey banding, sometimes very striking. Others are recrystallised to massive milky quartz with black chloritic banding, although John Richmond and others have found amethystine quartz in some. The greenish colouration appears to be due to fine inclusions of pumpellyite. Some small white to bright pink calcite veins occur in some nodules, and some of these contain some nice pale green, botryoidal prehnite to a cm or so thick. A little fine yellow-green epidote also appears to be present. The basalt itself appears to be altered to a dark green chlorite-amphibole-epidote rock.

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References