Dolerite is similar in composition to basalt, which is volcanic, and gabbro, which is plutonic.
[citation needed] Quartz dolerite is very common in central Scotland, in intrusive formations, sills and dykes, and is widely quarried for roadstone.
[citation needed] It was used with some success for making millstones at one time, the Millstone Grit part of the carboniferous strata not being present in Scotland, but it is no longer used for this purpose, and would probably be illegal now due to the formation of small quartz and other silicate particles, which could cause the serious respiratory disease silicosis.
In Scotland, quartz dolerite is commonly known as whin or whinstone.
[citation needed] Quartz dolerite contains many cooling fractures and weathers readily, becoming unstable.