Geoscience Reference
In-Depth Information
of several of England's most famous building stones,
including 'Ancaster', 'Barnack', 'Clipsham', and 'Ketton'.
They range in colour from pale whitish-brown to
yellowish-brown. Figure
47
is a general view of 'Ketton'
limestone, which is a classic oolitic limestone, being highly
porous and consisting entirely of ooliths. Ooliths in
limestones are rounded grains that form by accretion of
calcium carbonate around a nucleus. Figure
48
is a close
view of 'Ketton Stone' showing the concentric ring
structure of the ooliths. Figure
49
shows 'Ancaster Stone',
a porous, cream-buff-coloured oolitic limestone
(oobiosparite). Figure
50
shows 'Stamford Stone', a pale
buff-coloured, highly porous, bioclasic oolite limestone.
Figure
51
shows the blue/cream variety of 'Clipsham
Stone', which consists mainly of intraclasts that are well
cemented by sparite.
47
48
47
'Ketton' limestone (Lincolnshire, England)
consisting entirely of grain-supported ooliths (brown)
and with a high proportion of macropores (20%,
yellow/white); PPT, ×35.
48
Close view of 'Ketton' limestone showing
concentric ring structure of a calcareous oolith. The
brighter rings are more microporous than the darker
ones; UV, ×150.
49
50
49
'Ancaster' limestone (Lincolnshire, England)
consisting of grain-supported ooliths (dark brown) and
minor shell fragments, with a sparry calcite matrix
(pink) and a significant proportion of macropores
(15%); XPT, ×35.
50
'Stamford' limestone (Lincolnshire, England)
consisting of grain-supported shell fragments and
ooliths (brown), and with a high proportion of
macropores (20%, yellow); PPT, ×35.
