# Diabase

> Mediated Wiki article. Canonical URL: https://mediated.wiki/source/Diabase
> Markdown URL: https://mediated.wiki/source/Diabase.md
> Source: https://en.wikipedia.org/wiki/Diabase
> Source revision: 1345459248
> License: Creative Commons Attribution-ShareAlike 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/)

{{Short description|Type of igneous rock}}
thumb|Diabase
{{wikt | diabase}}

'''Diabase''' ({{IPAc-en|ˈ|d|aɪ|.|ə|ˌ|b|eɪ|s}}), also called '''dolerite''' ({{IPAc-en|ˈ|d|ɒ|l|.|ə|ˌ|r|aɪ|t}}) or '''microgabbro''',<ref name="Microgabbro">{{cite web |url=http://www.bgs.ac.uk/bgsrcs/rcs_details.cfm?code=DOLR |title=BGS Rock Classification Scheme - Dolerite (Synonymous with Microgabbro) |publisher=[British Geological Survey](/source/British_Geological_Survey) |access-date=24 August 2015 }}</ref> is a [mafic](/source/mafic), [holocrystalline](/source/holocrystalline), [subvolcanic rock](/source/subvolcanic_rock) chemically equivalent to [volcanic](/source/volcanic) [basalt](/source/basalt) or [pluton](/source/pluton)ic [gabbro](/source/gabbro). Diabase [dike](/source/Dike_(geology))s and [sill](/source/Sill_(geology))s are typically shallow intrusive bodies and often exhibit fine-grained to [aphanitic](/source/aphanitic) [chilled margin](/source/chilled_margin)s which may contain [tachylite](/source/tachylite) (dark mafic glass).

''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''.

==Etymology==
The name ''diabase'' comes from the French {{wikt-lang|fr|diabase}}, and ultimately from the Greek {{transl|grc|diabasis}} ({{wikt-lang|grc|διάβασις}} 'act of crossing over, transition'<ref>{{oed|diabase}}</ref>), whereas the name ''dolerite'' comes from the French {{wikt-lang|fr|dolérite}}, from the Greek {{transl|grc|dolerós}} ({{wikt-lang|grc|δολερός}} 'deceitful, deceptive'), because it was easily confused with [diorite](/source/diorite).

==Petrography==
[[File:Fair Head - geograph.org.uk - 817076.jpg|thumb|[Fair Head](/source/Fair_Head), Northern Ireland, a [sill](/source/sill_(geology)) of dolerite<ref name=Habitas>{{cite web |title=Earth Science Conservation Review: Fairhead |access-date=29 October 2025 |url=https://www.habitas.org.uk/escr/site.asp?Item=518}}</ref>]]
Diabase normally has a fine but visible [texture](/source/Rock_microstructure) of [euhedral](/source/euhedral) [lath](/source/lath)-shaped [plagioclase](/source/plagioclase) [crystal](/source/crystal)s (62%) set in a finer matrix of [clinopyroxene](/source/pyroxene), typically [augite](/source/augite) (20–29%), with minor [olivine](/source/olivine) (3% up to 12% in olivine diabase), [magnetite](/source/magnetite) (2%), and [ilmenite](/source/ilmenite) (2%).<ref>Klein, Cornelus and Cornelius S. Hurlbut Jr.(1986) ''[Manual of Mineralogy](/source/iarchive%3Amanualofmineralo00klei)'', Wiley, 20th ed., p. 483 {{ISBN|0-471-80580-7}}</ref> Accessory and alteration [mineral](/source/mineral)s include [hornblende](/source/hornblende), [biotite](/source/biotite), [apatite](/source/apatite), [pyrrhotite](/source/pyrrhotite), [chalcopyrite](/source/chalcopyrite), [serpentine](/source/serpentine_group), [chlorite](/source/chlorite_group), and [calcite](/source/calcite). The texture is termed ''diabasic'' and is typical of diabases. This diabasic texture is also termed ''interstitial''.<ref>Morehouse, W. W. (1959) ''The Study of Rocks in Thin Section'', Harper & Row, p. 160</ref> The [feldspar](/source/feldspar) is high in [anorthite](/source/anorthite) (as opposed to [albite](/source/albite)), the [calcium](/source/calcium) [endmember](/source/endmember) of the plagioclase anorthite-albite solid solution series, most commonly [labradorite](/source/labradorite).

==Locations==
[[File:Dike diabase AZ.jpg|thumb|A diabase [dike](/source/dike_(geology)) crosscutting horizontal [limestone](/source/limestone) beds in Arizona]]
[[File:Devil's Den 101215.jpg|thumb|Diabase boulders at [Devil's Den](/source/Devil's_Den) on the [Gettysburg Battlefield](/source/Gettysburg_Battlefield), Pennsylvania, US]]
[[File:Doleritfelsen und Köcherbäume.jpg|thumb|Dolerite rocks and [Quiver tree](/source/Quiver_tree)s near [Keetmanshoop](/source/Keetmanshoop) (Namibia)]]
[[File:Organ Pipes Mount Wellington.jpg|thumb|Dolerite forms tall vertical columns throughout [Tasmania](/source/Tasmania). These columns form steep vertical features through its alpine areas.]]

Diabase is usually found in smaller, relatively shallow intrusive bodies such as [dikes](/source/dike_(geology)) and [sill](/source/sill_(geology))s. Diabase dikes occur in regions of [crustal extension](/source/crustal_extension) and often occur in [dike swarm](/source/dike_swarm)s of hundreds of individual dikes or sills radiating from a single [volcanic](/source/volcanic) center.

The [Palisades Sill](/source/Palisades_Sill) which makes up the [New Jersey Palisades](/source/New_Jersey_Palisades) on the [Hudson River](/source/Hudson_River), near [New York City](/source/New_York_City), New York, United States, is an example of a diabase sill. The dike complexes of the [British Tertiary Volcanic Province](/source/British_Tertiary_Volcanic_Province) includes Skye, Rum, Mull, and Arran of western [Scotland](/source/Scotland), the [Slieve Gullion](/source/Slieve_Gullion) region of [Ireland](/source/Ireland), and dolerite dike swarms extending across northern [England](/source/England) towards the Midlands, for example [Rowley Rag](/source/Rowley_Rag). Parts of the [Deccan Traps](/source/Deccan_Traps) of India, formed at the end of the [Cretaceous](/source/Cretaceous), also include dolerite.<ref>[http://www.geokem.com/flood-basalts-1.html ''Continental Flood Basalts (and Layered Intrusions)'']</ref> It is also abundant in large parts of [Curaçao](/source/Cura%C3%A7ao), an island off the coast of [Venezuela](/source/Venezuela). Another example of diabase dikes has been recognized in the [Mongo](/source/Mongo%2C_Chad) area within the [Guéra Massif](/source/Gu%C3%A9ra_Region) of [Chad](/source/Chad) in Central Africa.<ref>{{Cite journal|last1=Nkouandou|first1=Oumarou Faarouk|last2=Bardintzeff|first2=Jacques-Marie|last3=Mahamat|first3=Oumar|last4=Fagny Mefire|first4=Aminatou|last5=Ganwa|first5=Alembert Alexandre|date=2017-05-22|title=The dolerite dyke swarm of Mongo, Guéra Massif (Chad, Central Africa): Geological setting, petrography and geochemistry|journal=Open Geosciences|volume=9|issue=1|pages=138–150|doi=10.1515/geo-2017-0012|issn=2391-5447|bibcode=2017OGeo....9...12N|doi-access=free}}</ref>

In the [Death Valley](/source/Death_Valley) region of California, [Precambrian](/source/Precambrian) diabase intrusions metamorphosed pre-existing [dolomite](/source/Dolomite_(mineral)) into economically important [talc](/source/talc) deposits.<ref>Miller, MB, and Wright, LA. 2007, "Geology of Death Valley National Park (Third Edition)", Kendall Hunt Publishing, p 19.</ref>

In the Thuringian-Franconian-Vogtland Slate Mountains of central [Germany](/source/Germany) the diabase is entirely of [Devonian](/source/Devonian) age.<ref name="Deutsch2006">{{cite book | title=Einführung in die Geologie Deutschlands | publisher=Spektrum Akademischer Verlag | first1=Dierk | last1=Henningsen | first2=Gerhard | last2=Katzung | year=2006 | edition=7th | location=Munich | page=69 | isbn=3-8274-1586-1 | language=de}}</ref> They form typical domed landscapes, especially in the [Vogtland](/source/Vogtland). One [geotourist](/source/Geotourism) attraction is the ''[Steinerne Rose](/source/Steinerne_Rose)'' near [Saalburg](/source/Saalburg-Ebersdorf), a natural monument, whose present shape is due to the typical weathering of lava pillows.

===Gondwanaland and Australia===
A [geological event](/source/geological_event) known as the [Oenpelli](/source/Oenpelli) Dolerite intrusive event occurred about 1,720 million years ago in western [Arnhem Land](/source/Arnhem_Land), in the [Northern Territory](/source/Northern_Territory),<ref>{{cite web|url=https://geoscience.nt.gov.au/gemis/ntgsjspui/bitstream/1/74562/1/EL5893_2008_P_01.pdf|title=Wellington Range Project Northern Territory EL 5893 Relinquishment Report|publisher=Cameco Australia Pty Lt|date=August 2008 |series=Report No.: WR08-02 |first1=Cath |last1=Ranford |first2=Paul|last2= Melville |first3=Craig|last3= Bentley|access-date=5 Oct 2020}}</ref> forming curved ridges of Oenpelli Dolerite stretching over {{convert|30,000| km2}}.<ref>{{cite web | website=Australian Stratigraphic Units Database|publisher= Australian Government. Geoscience Australia | title=Definition card for: Oenpelli Dolerite| url=http://dbforms.ga.gov.au/pls/www/geodx.strat_units.def?strno=14496&stratname=Oenpelli%20Dolerite | access-date=5 October 2020}} 50px Text was copied from this source, which is available under a [https://creativecommons.org/licenses/by/3.0/au/ Attribution 3.0 Australia (CC BY 3.0 AU)] licence.</ref> Further west, on the northern coast of Arnhem Land, a "subsurface radial dyke swarm" known as [Galiwinku](/source/Galiwinku) Dolerite, taking its name from the [Aboriginal](/source/Aboriginal_Australian) name for Elcho Island, occurs on the [Gove Peninsula](/source/Gove_Peninsula) and continues under the [Arafura Sea](/source/Arafura_Sea) and on [Wessel Islands](/source/Wessel_Islands), including Elcho and [Milingimbi Island](/source/Milingimbi_Island)s.<ref>{{cite web | website=Australian Stratigraphic Units Database|publisher= Australian Government. Geoscience Australia | title=Definition card for: Galiwinku Dolerite| url=http://dbforms.ga.gov.au/pls/www/geodx.strat_units.def?strno=77145&stratname=Galiwinku%20Dolerite | access-date=5 October 2020}} 50px Text was copied from this source, which is available under a [https://creativecommons.org/licenses/by/3.0/au/ Attribution 3.0 Australia (CC BY 3.0 AU)] licence.</ref>

In the [Yilgarn craton](/source/Yilgarn_craton) of [Western Australia](/source/Western_Australia), a [Proterozoic](/source/Proterozoic) {{convert|200| km |adj=on}} long dolerite dike, the [Norseman-Wiluna greenstone belt](/source/Norseman-Wiluna_greenstone_belt)<ref>Hill R.E.T, [Barnes S.J.](/source/Sarah-Jane_Barnes), 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. {{ISBN|0-909869-55-3}}</ref> is associated with the non-alluvial [gold](/source/gold) mining area between [Norseman](/source/Norseman%2C_Western_Australia) and [Kalgoorlie](/source/Kalgoorlie), which includes the largest gold mine in Australia,<ref>{{cite journal|doi=10.1144/1467-7873/07-132|author1=O'Connor-Parsons, Tansy |author2=Stanley, Clifford R. |title=Downhole lithogeochemical patterns relating to chemostratigraphy and igneous fractionation processes in the Golden Mile dolerite, Western Australia|year=2007|journal=Geochemistry: Exploration, Environment, Analysis|volume=7|issue=2|pages=109–27|bibcode=2007GEEA....7..109O |s2cid=140677224 }}</ref> the [Super Pit gold mine](/source/Super_Pit_gold_mine). West of the Norseman–Wiluna Belt is the [Yalgoo-Singleton greenstone belt](/source/Yalgoo-Singleton_greenstone_belt), where complex dolerite dike swarms obscure the volcaniclastic sediments.<ref>{{cite journal|author1=Wanga Q. |author2=Campbella I. H. |year= 1998|title= Geochronology of supracrustal rocks from the Golden Grove area, Murchison Province, Yilgarn Craton, Western Australia |journal=Australian Journal of Earth Sciences|doi=10.1080/08120099808728413|volume=45|issue=4|pages=571–77|bibcode = 1998AuJES..45..571W }}</ref> 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.<ref name="Travis_etal_1971">{{Citation|last1=Travis|first1=G.A.|last2=Woodall|first2=R.|last3=Bartram|first3=G.D.|chapter=The Geology of the Kalgoorlie Goldfield|editor-last=Glover|editor-first=J.E.|title=Symposium on Archaean Rocks|pages=175–190|publisher=Geological Society of Australia (Special Publication 3)|date=1971}}</ref>

The vast areas of mafic volcanism/[plutonism](/source/plutonism) associated with the [Jurassic](/source/Jurassic) breakup of the [Gondwana](/source/Gondwana) supercontinent in the [Southern Hemisphere](/source/Southern_Hemisphere) include many large diabase/dolerite sills and dike swarms. These include the [Karoo](/source/Karoo) dolerites of [South Africa](/source/South_Africa), the [Ferrar Dolerite](/source/Karoo-Ferrar)s of [Antarctica](/source/Antarctica), and the largest of these, the most extensive of all dolerite formations worldwide, are found in [Tasmania](/source/Tasmania). Here, the volume of [magma](/source/magma) which intruded into a thin veneer of [Permian](/source/Permian) and [Triassic](/source/Triassic) rocks from multiple feeder sites, over a period of perhaps a million years, may have exceeded 40,000 cubic kilometres.<ref>[Leaman, David](/source/David_Leaman) 2002, "The Rock that Makes Tasmania", Leaman Geophysics, {{ISBN|0-9581199-0-2}} p. 117.</ref> In Tasmania, dolerite dominates much of the landscape, particularly alpine areas, with many examples of [columnar jointing](/source/columnar_jointing).

[Early Jurassic](/source/Early_Jurassic) activity resulted in the formation of [dolerite intrusion in Prospect](/source/Prospect_dolerite_intrusion) in [Sydney](/source/Sydney),<ref>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.</ref> and [quarrying](/source/quarrying) of [basalt](/source/basalt) for [roadstone](/source/roadstone) and other building materials has been an important activity there for over 180 years.<ref name="Johnson1989">{{cite book|author=Robert Wallace Johnson|title=Intraplate Volcanism: In Eastern Australia and New Zealand|url=https://books.google.com/books?id=4NBOn7ecZeAC&pg=PA4|date=24 November 1989|publisher=Cambridge University Press|isbn=978-0-521-38083-6|pages=4–}}</ref><ref>Wilshire, H.G. (1967) The Prospect Alkaline Diabase-Picrite Intrusion New South Wales, Australia. Journal of Petrology 8(1) pp.97-163.</ref>

==Use==

Diabase is crushed and used as a [construction aggregate](/source/construction_aggregate) for road beds, buildings, railroad beds (rail ballast), and within dams and levees.<ref>{{cite web|last1=Allen|first1=George|title=Clayton Quarry|url=http://www.mdia.org/site/mining/clayton-quarry|publisher=Mount Diablo Interpretive Association|date=Spring 2004|access-date=2017-03-30|archive-url=https://web.archive.org/web/20171116184525/http://www.mdia.org/site/mining/clayton-quarry|archive-date=2017-11-16|url-status=dead}}</ref><ref name="comparerocks">{{cite web|title=Diabase Rock|url=http://www.comparerocks.com/en/diabase-rock/model-82-0|publisher=comparerocks.com|access-date=2017-03-30|archive-url=https://web.archive.org/web/20170331115113/http://www.comparerocks.com/en/diabase-rock/model-82-0|archive-date=2017-03-31|url-status=dead}}</ref>

Diabase can be cut for use as [headstone](/source/headstone)s and memorials; the base of the [Marine Corps War Memorial](/source/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.<ref name="comparerocks"/> A form of dolerite, known as [bluestone](/source/bluestone), is one of the materials used in the construction of [Stonehenge](/source/Stonehenge).<ref name="AGI_Stonehenge">{{cite web | url=https://www.earthmagazine.org/article/stonehenges-mysterious-stones | title=Stonehenge's Mysterious Stones | publisher=[American Geosciences Institute](/source/American_Geosciences_Institute) | work=Earth magazine | date=31 December 2008 | access-date=8 November 2019 | first1=Brian S. | last1=John | first2=Lionel E. | last2=Jackson Jr.}}</ref>

Diabase also serves as local building stone. In Tasmania, where it is one of the most common rocks found,<ref name="TasVitiGeoMap">{{cite web | url=https://dpipwe.tas.gov.au/Documents/Geology3.pdf | title=Tasmanian Viticultural Soils and Geology | publisher=Tasmania Department of Primary Industries, Water and Environment / University of Tasmania / Tasmanian Institute of Agricultural Research | access-date=8 November 2019}}</ref> it is used for building, for landscaping and to erect [dry-stone](/source/Dry_stone) farm walls. In northern [County Down](/source/County_Down), Northern Ireland, "dolerite" is used in buildings such as [Mount Stewart](/source/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.<ref name="Pounders">{{cite journal | title = Dolerite pounders: Petrology, sources, and use | journal = Lithic Technology | volume = 35 | issue = 2 | year = 2010 | pages = 127–148 | last1 = Kelany | first1 = Adel | last2 = Harrell | first2 = James A. | last3 = Brown | first3 = V. Max | doi = 10.1080/01977261.2010.11721087 | jstor = 23273763 | s2cid = 127942498 | url = https://www.jstor.org/stable/23273763 | quote = Dolerite pounders are hand-held stone tools that were widely used in Egypt from the third to late first millennium BCE for quarrying and dressing granite and other hard rocks.| url-access = subscription }}</ref>

==See also==
* [List of rock types](/source/List_of_rock_types)
{{clear}}

==References==
{{Reflist|30em}}

==External links==
{{Commons category|Diabase}}
{{EB1911 poster|Diabase}}
*[https://maps.google.com/?ie=UTF8&ll=-27.798084,17.582932&spn=0.115559,0.222301&t=h&z=13 Collection of dikes in the Fish River Canyon, Namibia]

{{Igneous rocks}}
{{Rock type}}
{{Authority control}}

Category:Aphanitic rocks
Category:Ophitic rocks
Category:Mafic rocks
Category:Subvolcanic rocks

---
Adapted from the Wikipedia article [Diabase](https://en.wikipedia.org/wiki/Diabase) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Diabase?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.