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It is a "convenience" label rather than a geological term, since at least 46 different rock types are represented. One of the most common rocks in the assemblage is known as Preseli Spotted Dolerite—a chemically altered igneous rock containing spots or clusters of secondary minerals replacing plagioclase feldspar. It is a medium grained dark ...
It consists of a series of outcrops of spotted dolerite similar to that of other tors in the area, and several other prehistoric sites have been identified nearby. The mountain-top setting provides commanding views across the surrounding countryside and across Cardigan Bay to the Llŷn Peninsula .
Diabase (/ ˈ d aɪ. ə ˌ b eɪ s /), also called dolerite (/ ˈ d ɒ l. ə ˌ r aɪ t /) or microgabbro, [1] is a mafic, holocrystalline, subvolcanic rock equivalent to volcanic basalt or plutonic gabbro.
However, in 2015, researchers reported they had confirmed the Preseli Spotted Dolerite stones at Stonehenge came from two Neolithic quarries at Carn Goedog and Craig Rhos-y-felin in the Preseli Hills. Using radiocarbon dating, researchers dated the quarry activities to around 3400 BC for Craig Rhos-y-felin and 3200 BC for Carn Goedog.
It is estimated that the quarrying, fashioning, transport and construction of such an amount represents about four work days for a single worker (assuming a 10-hour day). The original monument, Cairn 1, had a volume of about 2,000 cubic metres; it is built of 1,000 tons of granite and 3,000 tons of dolerite.
Stone was quarried from a sill of dolerite rock, which was the result of lava rising through the strata of the surrounding limestone 'Derbyshire Dome'. Tideswell Dale is part of the designated Wye Valley Site of Special Scientific Interest (SSSI) between Buxton and Bakewell , which also covers Cunning Dale, Woo Dale, Wye Dale, Chee Dale ...
The Jersey Main Dyke Swarm consists of dolerite dykes intruded into the South East Igneous complex. Some dolerite dykes have a porphyry centre. The strike is north-west, and the direction is vertical. Augite and labradorite are found in these dolerites. In the north-west there are sills of dolerite.
This was two days before his lookout spotted Tasmania for the first time. This was the first prognostication of mineral wealth on the west coast of Tasmania. A. W. Humphrey, a mineralogist, collected rocks and minerals from 1804. W. H. Twelvetrees and W. F. Petterd did petrographic investigations in Cygnet, around 1899. [21]