|Sandstone is a sedimentary rock made up of cemented sand sized grains of minerals. The most common constituent is quartz, followed by the mineral feldspar. Sandstones are the most common building materials in Herefordshire and Worcestershire and so make up a large number of buildings.
|Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate (CaCO3). Most limestone is composed of skeletal fragments of marine organisms such as coral, forams and molluscs.
|Siltstone is a sedimentary rock with a finer grain size than sandstone. Individual grains are at the limit of what is visible with the naked eye. In several areas there is a continuum between limestone and siltstone depending on the amount of calcium carbonate in the rocks.
|Igneous rocks are those formed by the solidification of molten magma or lava. Examples include granite, basalt and diorite.
|Metamorphic rocks are formed by the alteration of igneous or sedimentary rocks by exposure to elevated temperatures and/or pressures. The change in conditions causes the minerals in the rock to change to new ones. Examples of metamorphic rocks include slate and marble.