| Back | Main Details | Samples & Images | Quarries | Usage | References |
| Local Name(s): |
Portland Whit Bed, Portland Brown Bed. |
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| Stone Group: | Sedimentary | ||||||
| Stone Type: | Limestone | ||||||
| Geology: |
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| Geological Sub-Divisons: | Portland Formation, Portland Stone Member (Portland Stone). Three main beds are important:- Roach (normally top of the series), Whit Bed (middle) and Base Bed (lower). |
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| General Colour Description: | A warm cream/brown to pale brown tint when fresh which becomes white on exposure |
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| Hand Specimen Description: | A hard, moderately well sorted, oolitic limestone containing variable shell fragments (similar to those in Portland Roach) but less common. The oolitic structure is very marked. |
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| Petrographic Description: | A fine grained oolitic limestone (95% calcium carbonate, 1% quartz) comprising white to cream oolites (some of which are fused), broken shell debris (shell fragments are elongated to rounded and up to 5mm across) and occasional tiny quartz grains. It is formed from micrite ooids with a small quantity of micrite occuring as a matrix. The small broken shells are evenly distributed comprising oysters, bivalves, alga and large ammonites. |
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| General Comments: | In use, both Portland Whit Bed and Portland Base Bed can be indistinguishable. |
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| Stone Identifiers: | Fossiliferous, Oolitic. | ||||||
| Reacts dilute to HCl? | Yes | ||||||
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