Dorset Stone Company Ltd

t/a Marnhull Stone Quarries. Tel: 01258 820712

For those interested in building stone sourced from Dorset, the following link will download English Heritage's excellent paper on the subject...


Strategic Stone Study - A Building Stone Atlas of Dorset


English Heritage


Stone Terminology (courtesy of Dorset Strategic Stone Study)


Stone masonry comprising blocks with carefully worked beds and joints, finely jointed (generally under 6mm) and set in horizontal courses. Stones within each course are of the same height, though successive courses may be of different heights. ‘Ashlar’ is often wrongly used as a synonym for facing stone.

Bioclastic limestone:

A limestone composed of fragments of calcareous organisms.


A mineral made of calcium, carbon and oxygen — CaCO3 ; the principle carbonate component of limestone, chalk and marble.


The diagenetic process by which the constituent framework grains of a rock are bound together by minerals precipitated from associated pore fluids (e.g. quartz and calcite).


A very fine-grained white limestone composed principally of microscopic skeletal remnants known as coccoliths.


A granular microcrystalline to cryptocrystalline variety of quartz.


To say a building is constructed of brick with stone dressings means that worked stone frames the corners and openings of the structure.


Containing iron minerals usually in the form of an iron oxide which gives the rock a ‘rusty’ stain.

Flint (or Chert):

Hard, resistant beds or nodules composed of cryptocrystalline silica. The use of the term flint is restricted to nodules and beds that occur only in Chalk (Upper Cretaceous) rocks.

Fossiliferous: Bearing or containing fossils.

Freestone: Term used by masons to describe a rock that can be cut and shaped in any direction without splitting or failing.


Occurs when beds (layers or rock) of a particular lithology lie between or alternate with beds of a different lithology. For example, sedimentary rocks may be interbedded if there were sea level variations in their sedimentary depositional environment.


A sedimentary rock consisting mainly of calcium carbonate (CaCO3 ) grains such as ooids, shell and coral fragments and lime mud. Often highly fossiliferous.


The description of a rock based on its mineralogical composition and grain-size e.g. sandstone, limestone, mudstone etc.


Rocks which have been subject to heat and/or pressure which has caused changes in their solid state e.g. mudstone to slate, limestone to marble.


Limestone consisting of microcrystalline calcite mud or a very finely crystalline carbonate cement.


Anything with a contour or section, either projecting or inset, to give emphasis, usually to horizontal and vertical lines.


A fine-grained sedimentary rock composed of a mixture of clay and silt-sized particles.


A spheroidal grain of calcium carbonate formed by precipitation (by algae) of calcium carbonate in concentric layers. Outcrop: Area where a rock unit is exposed at the ground surface.


The ratio of the fraction of voids to the volume of rock in which they occur.


Rough, undressed or roughly dressed building stones typically laid uncoursed (random rubble) or brought to courses at intervals. In squared rubble, the stones are dressed roughly square, and typically laid in courses (coursed squared rubble).


A sedimentary rock composed of sandsized grains (i.e. generally visible to the eye, but less than 2 mm in size)

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