St. Bees

Submitted by Ed FitzGerald on Tue, 2015-03-10 09:40
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St. Bees is a dark red sandstone of Permo Triassic age, which forms the sea cliffs of St. Bees Head near Whitehaven in Cumbria, UK.

Physical Data
Stone Type (Lithologic): 
Grain Shape: 
Grain Sorting: 
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Petrographic Description: 

Specimen: 2015-004
This specimen is a sandstone. Detrital grains constitute about 75 percent of slide area, void space is approximately 10 to 15 percent, and the remaining area is occupied by fine grained matrix. Much of the void space is potentially the result of recent weathering or even slide preparation, formally filled by matrix. Most grains are subrounded to subangular. Of the detrital grains, quartz comprises about 60 percent of grains. Feldspars predominate among the remaining portion with opaques, micas, and lithic fragments contributing minimally. Based on these estimates this sandstone is classified as a feldspathic greywacke (this assumes much of the void space was originally fine-grained matrix). The constituent grains are well sorted. These observations suggest the parent material of detrital grains was mineralogically immature. Textural maturity is submature. Maximum grain size is .3 mm and minimum is .02 mm. The modal size is around .15 mm. Preserved matrix cement is predominantly composed of iron oxides/hydroxides and clay minerals, carbonates are also visible in some intergrain spaces and may be prevalent in less weathered samples. The cementing medium is what imparts the red color to the stone. There is a thin band of better preserved cementing medium with a relatively high iron mineral content about .6 mm wide. No visible macrostructure, such as bedding is visible in thin section. The hand sample presents only faint banding that is unlikely to be evident in a thin section.
MP 9/5/2014


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Specimen ID
2015-004 Image of specimen in dry conditions. Finish: Smooth sawndownload image Image of specimen in wet conditions. Finish: Smooth sawndownload image

Thin Sections

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Specimen ID Non-polarized Cross-polarized
2015-004 Specimen shown in non-polarized image Specimen shown in cross-polarized image


NOTE: Quarry locations are approximate.

Birkham's Quarry
United Kingdom
54° 31' 21.036" N, 3° 37' 5.52" W
Cumbria GB

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