Pitchstone

The pitchstone ridge An Sgùrr in Eigg, Scotland

Pitchstone is a dull black glassy volcanic rock formed when felsic lava or magma cools quickly. It is a volcanic glass; however, unlike a glass, pitchstone has an irregular hackly fracture not a conchoidal fracture. That is due to its coarser (than obsidian) crystal structure. Pitchstone has a resinous lustre, or silky in some cases, and a variable composition. Its colour may be mottled, streaked, or uniform brown, red, green, gray, or black. It is an extrusive rock that is very resistant to erosion.^[1]

The pitchstonen ridge of An Sgùrr on the Isle of Eigg, Scotland, was possibly formed as a lava flow in a valley.^[2]

Pitchstone from the Isle of Arran was used as the raw material for making various items from the Mesolithic through the Neolithic to the Early Bronze Age.^[3] Mesolithic use appears to have been limited to the Isle of Arran itself, while in later periods the material or items made from it were transported around Britain.^[3]

References[]

^ Troll, Valentin R.; Emeleus, C. Henry; Nicoll, Graeme R.; Mattsson, Tobias; Ellam, Robert M.; Donaldson, Colin H.; Harris, Chris (2019-01-24). "A large explosive silicic eruption in the British Palaeogene Igneous Province". Scientific Reports. 9 (1): 494. Bibcode:2019NatSR...9..494T. doi:10.1038/s41598-018-35855-w. ISSN 2045-2322. PMC 6345756. PMID 30679443.
^ al.], C.H. Emeleus ; contributors: J.D. Hudson ... [et (1997). Geology of Rum and the adjacent islands : memoir for 1:50000 geological sheet 60 (Scotland) (1. publ. ed.). London: Stationery Office. ISBN 0118845179. {{cite book}}: |first1= has generic name (help)
^ ^a ^b Ballin, Torben Bjarke (2015). "Arran pitchstone (Scottish volcanic glass): New dating evidence". Journal of Lithic Studies. University of Edinburgh. 2 (1): 5–16. doi:10.2218/jls.v2i1.1166.

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[1] Troll, Valentin R.; Emeleus, C. Henry; Nicoll, Graeme R.; Mattsson, Tobias; Ellam, Robert M.; Donaldson, Colin H.; Harris, Chris (2019-01-24). "A large explosive silicic eruption in the British Palaeogene Igneous Province". Scientific Reports. 9 (1): 494. Bibcode:2019NatSR...9..494T. doi:10.1038/s41598-018-35855-w. ISSN 2045-2322. PMC 6345756. PMID 30679443.

[2] .], C.H. Emeleus ; contributors: J.D. Hudson ... [et (1997). Geology of Rum and the adjacent islands : memoir for 1:50000 geological sheet 60 (Scotland) (1. publ. ed.). London: Stationery Office. ISBN 0118845179. {{cite book}}: |first1= has generic name (help)

[ballin-3] Ballin, Torben Bjarke (2015). "Arran pitchstone (Scottish volcanic glass): New dating evidence". Journal of Lithic Studies. University of Edinburgh. 2 (1): 5–16. doi:10.2218/jls.v2i1.1166.

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