GEOLOGICAL BACKGROUND

Formation of Clipsham Stone

Clipsham Stone is a member of the Lincolnshire Limestone deposits. These deposits occur in the Inferior Oolite of the Jurassic system.  This Limestone was probably deposited in a moderately sub-tropical sea, where changes were frequent,  making its texture liable to a certain amount of variation.

When dry, the colour of Clipsham Stone may vary between pale cream and buff. The ground colour of the stone from the Old Quarry is buff and there are small spots or patches of a light brown colour. It is coarse-grained and somewhat oolitic and among the clastic are very small pebbles and large numbers of shell fragments.

Throughout the whole mass of the stone are large numbers of plates of calcite, which give it a peculiar glistening appearance. The matrix under an ordinary hand lens has an earthy appearance, but if examined by the microscope it is found to be crystalline; it consists of calcite.

The ooliths are of a variety of shapes and there are also in this stone numbers of shell fragments and some very small pebbles. Among the shell fragments are portions of encrinites and echinoderms. Scattered in the mass of the stone are numbers of glistening crystals of calcite and the whole of the clastic is bound together by a matrix of the same material. On a faced surface of this stone a great number of the fragmentary particles appear somewhat greyish and opaque.

Glossary of terms for the not so technical:

Calcite White or colourless mineral consisting of calcium carbonate. Encrinites a sedimentary rock formed almost exclusively from the skeletal plates of crinoids.
Clastic Rocks composed of broken pieces of older rocks. Jurassic Approx. 208 – 146 million years ago.
Echinoderms Marine invertebrates. Oolite Limestone consisting of a mass of rounded grains (ooliths) made up of concentric layers.

 

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