Oolitic limestone - Weldon
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Fact sheet

Oolitic limestone - Weldon

This building stone was collected from the Weldon quarries near Corby, Northamptonshire. The rock is formed of many small shell fragments and spherical (ooid) or elongate (pelloid) concretions. This rock formed during the Jurassic period; however, similar rocks are still being formed today in warm shallow modern oceans around areas such as the Bahamas. Their formation occurs in shallow marine seas, encouraged by factors such as high calcium carbonate concentrations, agitation of the ooids and pelloids (rolling around on the sea floor maintains the rounded shapes), and probably the action of microbes in precipitation of the coatings.

The thin section contains many open pore spaces as a result of the grains and shell fragments being given rounded shapes by coatings of very fine-grained micrite. Each ooid has a fragment of sand at its core. Other, more elongate pelloid grains formed when mineral and shell fragments were rolled around in the same environment. The largest shell fragments are clearly made of more coarsely crystalline calcite and lie parallel to the original sea floor. While they are not as completely or as evenly coated as the smaller fragments, they nevertheless received some coating before deposition.

Additional images
  • oolitic limestone
  • oolitic limestone - width 3 cm
  • oolitic limestone - width 13 cm
52.4866, -0.6422
Weldon quarries, near Corby, Northamptonshire
About this collection

The United Kingdom Virtual Microscope (UKVM) collection consists of igneous, sedimentary and metamorphic rocks from around the UK.

It is intended as a teaching resource, helping to tell the story of the common rock types and how they form, and reflecting the history of the UK at the margins of the continent of Europe. The collection is a series of teaching sets, for example igneous rocks from the North Atlantic Igneous Province and SW England; high-temperature metamorphic rocks from Scotland and low-temperature metamorphic rocks from Wales; and sedimentary rocks, including English limestones and sandstones.

Sample details

Rock-forming mineral
Category guide  
Category Guide
Refers to any word or phrase that appears in the individual rock names. Names are generally descriptive; they allow users to search for broad terms like ‘granite’ as well as more specific names such as ‘breccia’. However, the adjacent descriptions of the specimens captures a wider range of general words and phrases and is a more powerful search tool.
Refers to any word or phrase that appears anywhere in the descriptions of the specimens
Accessory minerals
Minerals that occur in very low abundance in a rock. They are usually not visible with the naked eye and contribute perhapssver, they often dominate the rare elements such as platinum group metals.
Rock-forming minerals
Minerals that make up the bulk of all rock samples and are also the ones used in rock classi?cation.
Selecting one or more period, for example 'Jurassic'.
A term used to group together related samples that are not already gathered into a single Collection. For instance, there is a ‘SW England granites’ theme that includes such rock types as granite, hydrothermal breccia, skarn and vein samples.
A general term used to label a rock sample. It is a useful way of grouping similar samples throughout a collection. Category names are often, but not exclusively, common rock names (e.g. granite, basalt, dolerite, gabbro, greisen, skarn, gneiss, amphibolite, limestone, sandstone).
The owner of the sample that appears in the collection. For example, NASA owns all the samples that appear in the Moon Rocks collection
We would like to thank the following for the use of this sample: