Dolerite – Skye

Dolerite is a mafic igneous rock which forms as intrusive sills or dykes which are often shallow, close to the earth surface and considered to be sub-volcanic rocks. Known as diabase in North America, it often has a fine crystalline texture and is composed of expected mafic minerals such as pyroxenes, usually augite crystals with occurrences of olivine, magnetite and ilmenite, usually iron bearing minerals which give the rock a dark appearance. These minerals often make up the fine grained matrix in which plagioclase crystals may be set in, as such, these particular rock samples, which come from Torrin, Isle of Skye, Scotland, UK, exhibit a highly crystalline appearance, black colouration and density. A tough rock, the samples are almost glass like when broken due to the fine texture and are believed to have formed during the Tertiary period and came into contact with Skye marble, resulting in metasomatism occurring due to contact between the sill and marble. The samples are suitable for the more serious collector to complete igneous collections or those interested in Scottish and British samples. However, the specimens are also excellent for higher educational use to display the different groups of igneous rock which students may encounter in the field. Samples are available in three sizes and come supplied in a card tray with an information label.