This is a bio-oo-micrite. It is from the Portland Limestone. It has been partly silicified and the thin section straddles the boundary between limestone and chert nodule.
This collection of virtual thin sections is the result of a collaboration between earth scientists at Portsmouth University and The Open University. The collection consists of 26 slides from the Portsmouth teaching collection, including igneous, metamorphic and sedimentary rocks.
UNDER CONSTRUCTION! This Collection is currently under development, so you may notice reduced functionality as new samples are brought online.