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Diabase (), also called dolerite () or microgabbro,
Diabase is the preferred name in North America, while dolerite is the preferred name in the rest of the English-speaking world, where sometimes the name diabase refers to altered dolerites and basalts. Some geologists prefer to avoid confusion by using the name microgabbro.
The name diabase comes from the French diabase, and ultimately from the Greek διάβασις 'act of crossing over, transition', whereas the name dolerite comes from the French dolérite, from the Greek δολερός 'deceitful, deceptive', because it was easily confused with diorite.
The Palisades Sill which makes up the New Jersey Palisades on the Hudson River, near New York City, New York, United States, is an example of a diabase sill. The dike complexes of the British Tertiary Volcanic Province includes Skye, Rum, Mull, and Arran of western Scotland, the Slieve Gullion region of Ireland, and dolerite dike swarms extending across northern England towards the Midlands, for example Rowley Rag. Parts of the Deccan Traps of India, formed at the end of the Cretaceous, also include dolerite. Continental Flood Basalts (and Layered Intrusions) It is also abundant in large parts of Curaçao, an island off the coast of Venezuela. Another example of diabase dikes has been recognized in the Mongo area within the Guéra Massif of Chad in Central Africa.
In the Death Valley region of California, Precambrian diabase intrusions metamorphosed pre-existing dolomite into economically important talc deposits.Miller, MB, and Wright, LA. 2007, "Geology of Death Valley National Park (Third Edition)", Kendall Hunt Publishing, p 19.
In the Thuringian-Franconian-Vogtland Slate Mountains of central Germany the diabase is entirely of Devonian age. (2025). 9783827415868, Spektrum Akademischer Verlag. ISBN 9783827415868 They form typical domed landscapes, especially in the Vogtland. One Geotourism attraction is the Steinerne Rose near Saalburg, a natural monument, whose present shape is due to the typical weathering of lava pillows.
In the Yilgarn craton of Western Australia, a Proterozoic long dolerite dike, the Norseman-Wiluna greenstone beltHill R.E.T, Barnes S.J., Gole M.J., and Dowling S.E., 1990. Physical volcanology of komatiites; A field guide to the komatiites of the Norseman-Wiluna Greenstone Belt, Eastern Goldfields Province, Yilgarn Block, Western Australia., Geological Society of Australia. is associated with the non-alluvial gold mining area between Norseman and Kalgoorlie, which includes the largest gold mine in Australia, the Super Pit gold mine. West of the Norseman–Wiluna Belt is the Yalgoo-Singleton greenstone belt, where complex dolerite dike swarms obscure the volcaniclastic sediments. Large dolerite sills such as the Golden Mile Dolerite can exhibit coarse-grained texture, and show a large diversity in petrography and geochemistry across the width of the sill.
The vast areas of mafic volcanism/plutonism associated with the Jurassic breakup of the Gondwana supercontinent in the Southern Hemisphere include many large diabase/dolerite sills and dike swarms. These include the Karoo dolerites of South Africa, the Karoo-Ferrar of Antarctica, and the largest of these, the most extensive of all dolerite formations worldwide, are found in Tasmania. Here, the volume of magma which intruded into a thin veneer of Permian and Triassic rocks from multiple feeder sites, over a period of perhaps a million years, may have exceeded 40,000 cubic kilometres.David Leaman 2002, "The Rock that Makes Tasmania", Leaman Geophysics, p. 117. In Tasmania, dolerite dominates much of the landscape, particularly alpine areas, with many examples of columnar jointing.
Early Jurassic activity resulted in the formation of dolerite intrusion in Prospect in Sydney,Jones, I., and Verdel, C. (2015). Basalt distribution and volume estimates of Cenozoic volcanism in the Bowen Basin region of eastern Australia: Implications for a waning mantle plume. Australian Journal of Earth Sciences, 62(2), 255–263. and quarrying of basalt for roadstone and other building materials has been an important activity there for over 180 years.Wilshire, H.G. (1967) The Prospect Alkaline Diabase-Picrite Intrusion New South Wales, Australia. Journal of Petrology 8(1) pp.97-163.
Diabase can be cut for use as and memorials; the base of the Marine Corps War Memorial is made of black diabase "granite" (a commercial term, not actual granite). Diabase can also be cut for use as ornamental stone for countertops, facing stone on buildings, and paving. A form of dolerite, known as bluestone, is one of the materials used in the construction of Stonehenge.
Diabase also serves as local building stone. In Tasmania, where it is one of the most common rocks found, it is used for building, for landscaping and to erect Dry stone farm walls. In northern County Down, Northern Ireland, "dolerite" is used in buildings such as Mount Stewart together with Scrabo Sandstone as both are quarried at Scrabo Hill.
Balls of diabase were used by the ancient Egyptians as pounding tools for working softer (but still hard) stones.
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