Diorite ( ) is an
intrusive igneous rock
Igneous rock (derived from the Latin word ''ignis'' meaning fire), or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rock is formed through the cooling and solidification of magma o ...
formed by the slow cooling underground of
magma
Magma () is the molten or semi-molten natural material from which all igneous rocks are formed. Magma is found beneath the surface of the Earth, and evidence of magmatism has also been discovered on other terrestrial planets and some natural sa ...
(molten rock) that has a moderate content of
silica
Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , most commonly found in nature as quartz and in various living organisms. In many parts of the world, silica is the major constituent of sand. Silica is ...
and a relatively low content of
alkali metals. It is
intermediate in composition between low-silica (
mafic
A mafic mineral or rock is a silicate mineral or igneous rock rich in magnesium and iron. Most mafic minerals are dark in color, and common rock-forming mafic minerals include olivine, pyroxene, amphibole, and biotite. Common mafic rocks incl ...
)
gabbro and high-silica (
felsic)
granite
Granite () is a coarse-grained ( phaneritic) intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly cools and solidifies under ...
.
Diorite is found in mountain-building belts (''
orogen
An orogenic belt, or orogen, is a zone of Earth's crust affected by orogeny. An orogenic belt develops when a continental plate crumples and is uplifted to form one or more mountain ranges; this involves a series of geological processes collecti ...
s'') on the margins of continents. It has the same composition as the fine-grained volcanic rock,
andesite
Andesite () is a volcanic rock of intermediate composition. In a general sense, it is the intermediate type between silica-poor basalt and silica-rich rhyolite. It is fine-grained (aphanitic) to porphyritic in texture, and is composed predo ...
, which is also common in orogens.
Diorite has been used since prehistoric times as decorative stone. It was used by the
Akkadian Empire
The Akkadian Empire () was the first ancient empire of Mesopotamia after the long-lived civilization of Sumer. It was centered in the city of Akkad () and its surrounding region. The empire united Akkadian and Sumerian speakers under one ...
of
Sargon of Akkad for funerary sculptures, and by many later civilizations for sculptures and building stone.
Description
Diorite is an
intrusive igneous rock
Igneous rock (derived from the Latin word ''ignis'' meaning fire), or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rock is formed through the cooling and solidification of magma o ...
composed principally of the
silicate mineral
Silicate minerals are rock-forming minerals made up of silicate groups. They are the largest and most important class of minerals and make up approximately 90 percent of Earth's crust.
In mineralogy, silica (silicon dioxide, ) is usually consid ...
s
plagioclase
Plagioclase is a series of tectosilicate (framework silicate) minerals within the feldspar group. Rather than referring to a particular mineral with a specific chemical composition, plagioclase is a continuous solid solution series, more pro ...
feldspar
Feldspars are a group of rock-forming aluminium tectosilicate minerals, also containing other cations such as sodium, calcium, potassium, or barium. The most common members of the feldspar group are the ''plagioclase'' (sodium-calcium) felds ...
(typically
andesine
Andesine is a silicate mineral, a member of the plagioclase feldspar solid solution series. Its chemical formula is ( Ca, Na)( Al, Si)4 O8, where Ca/(Ca + Na) (% anorthite) is between 30–50%. The formula may be written as Na0.7-0.5Ca0.3-0.5Al ...
),
biotite,
hornblende
Hornblende is a complex inosilicate series of minerals. It is not a recognized mineral in its own right, but the name is used as a general or field term, to refer to a dark amphibole. Hornblende minerals are common in igneous and metamorphic rock ...
, and sometimes
pyroxene. The
chemical composition of diorite is
intermediate, between that of
mafic
A mafic mineral or rock is a silicate mineral or igneous rock rich in magnesium and iron. Most mafic minerals are dark in color, and common rock-forming mafic minerals include olivine, pyroxene, amphibole, and biotite. Common mafic rocks incl ...
gabbro and
felsic granite
Granite () is a coarse-grained ( phaneritic) intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly cools and solidifies under ...
.
It is distinguished from gabbro on the basis of the composition of the plagioclase species; the plagioclase in diorite is richer in
sodium
Sodium is a chemical element with the symbol Na (from Latin ''natrium'') and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 of the periodic table. Its only stable ...
and poorer in
calcium
Calcium is a chemical element with the symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar t ...
.
Geologists use rigorous quantitative definitions to classify coarse-grained igneous rocks, based on the mineral content of the rock. For igneous rocks composed mostly of silicate minerals, and in which at least 10% of the mineral content consists of
quartz
Quartz is a hard, crystalline mineral composed of silica ( silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical ...
, feldspar, or
feldspathoid
The feldspathoids are a group of tectosilicate minerals which resemble feldspars but have a different structure and much lower silica content. They occur in rare and unusual types of igneous rocks, and are usually not found in rocks containing prim ...
minerals, classification begins with the
QAPF diagram
A QAPF diagram is a double ternary diagram which is used to classify igneous rocks based on mineralogic composition. The acronym QAPF stands for "Quartz, Alkali feldspar, Plagioclase, Feldspathoid (Foid)". These are the mineral groups used f ...
. The relative abundances of quartz (Q),
alkali feldspar (A), plagioclase (P), and feldspathoid (F), are used to plot the position of the rock on the diagram.
[ The rock will be classified as either a dioritoid or a gabbroid if quartz makes up less than 20% of the QAPF content, feldspathoid makes up less than 10% of the QAPF content, and plagioclase makes up more than 65% of the total feldspar content. Dioritoids are distinguished from gabbroids by an anorthite (calcium plagioclase) fraction of their total plagioclase of less than 50%.
The composition of the plagioclase cannot easily be determined in the field, and then a preliminary distinction is made between dioritoid and gabbroid based on the content of mafic minerals. A dioritoid typically has less than 35% mafic minerals, typically including hornblende, while a gabbroid typically has over 35% mafic minerals, mostly pyroxenes or olivine. The name ''diorite'' (from ]Ancient Greek
Ancient Greek includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages (), the Archaic p ...
, "to distinguish") was first applied to the rock by René Just Haüy
René Just Haüy () FRS MWS FRSE (28 February 1743 – 1 June 1822) was a French priest and mineralogist, commonly styled the Abbé Haüy after he was made an honorary canon of Notre Dame. Due to his innovative work on crystal structure and hi ...
on account of its characteristic, easily identifiable large crystals of hornblende.[
Dioritoids form a family of rock types similar to diorite, such as monzodiorite, quartz diorite, or nepheline-bearing diorite. Diorite itself is more narrowly defined, as a dioritoid in which quartz makes up less than 5% of the QAPF content, feldspathoids are not present, and plagioclase makes up more than 90% of the feldspar content.]
Diorite may contain small amounts of quartz, microcline, and olivine
The mineral olivine () is a magnesium iron silicate with the chemical formula . It is a type of nesosilicate or orthosilicate. The primary component of the Earth's upper mantle, it is a common mineral in Earth's subsurface, but weathers quickl ...
. Zircon
Zircon () is a mineral belonging to the group of nesosilicates and is a source of the metal zirconium. Its chemical name is zirconium(IV) silicate, and its corresponding chemical formula is Zr SiO4. An empirical formula showing some of t ...
, apatite, titanite, magnetite, ilmenite
Ilmenite is a titanium-iron oxide mineral with the idealized formula . It is a weakly magnetic black or steel-gray solid. Ilmenite is the most important ore of titanium and the main source of titanium dioxide, which is used in paints, printing ...
, and sulfides occur as accessory minerals. Varieties deficient in hornblende and other dark minerals are called ''leucodiorite''. A ''ferrodiorite'' is a dioritoid enriched in iron
Iron () is a chemical element with Symbol (chemistry), symbol Fe (from la, Wikt:ferrum, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 element, group 8 of the periodic table. It is, Abundanc ...
and titanium
Titanium is a chemical element with the Symbol (chemistry), symbol Ti and atomic number 22. Found in nature only as an oxide, it can be reduced to produce a lustrous transition metal with a silver color, low density, and high strength, resista ...
. Ferrodiorites are common in the lower oceanic crust.
Coarse-grained ( phaneritic) dioritoids are produced by slow crystallization of magma
Magma () is the molten or semi-molten natural material from which all igneous rocks are formed. Magma is found beneath the surface of the Earth, and evidence of magmatism has also been discovered on other terrestrial planets and some natural sa ...
having the same composition as the lava
Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a moon onto its surface. Lava may be erupted at a volcano or through a fracture in the crust, on land or un ...
that solidifies rapidly to form fine-grained (aphanitic
Aphanites (adj. ''aphanitic''; ) are igneous rocks that are so fine-grained that their component mineral crystals are not visible to the naked eye (in contrast to phanerites, in which the crystals are visible to the unaided eye). This geolog ...
) andesite
Andesite () is a volcanic rock of intermediate composition. In a general sense, it is the intermediate type between silica-poor basalt and silica-rich rhyolite. It is fine-grained (aphanitic) to porphyritic in texture, and is composed predo ...
. Rock of similar composition to diorite or andesite but with an intermediate texture is sometimes called ''microdiorite''. Diorite is occasionally porphyritic. It usually contains enough mafic minerals to be dark in appearance. ''Orbicular diorite'' shows alternating concentric growth bands of plagioclase and amphibole surrounding a nucleus, within a diorite porphyry matrix.
Occurrence
Diorite results from the partial melting
Partial melting occurs when only a portion of a solid is melted. For mixed substances, such as a rock containing several different minerals or a mineral that displays solid solution, this melt can be different from the bulk composition of the soli ...
of a mafic rock above a subduction zone. It is found in volcanic arc
A volcanic arc (also known as a magmatic arc) is a belt of volcanoes formed above a subducting oceanic tectonic plate,
with the belt arranged in an arc shape as seen from above. Volcanic arcs typically parallel an oceanic trench, with the arc lo ...
s, and in cordilleran mountain building, such as in the Andes Mountains. However, while its extrusive
Extrusive rock refers to the mode of igneous volcanic rock formation in which hot magma from inside the Earth flows out (extrudes) onto the surface as lava or explodes violently into the atmosphere to fall back as pyroclastics or tuff. In contra ...
volcanic
A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface.
On Earth, volcanoes are most often found where tectonic plates a ...
equivalent, andesite, is common in these settings, diorite is a minor component of the plutonic rocks, which are mostly granodiorite
Granodiorite () is a coarse-grained ( phaneritic) intrusive igneous rock similar to granite, but containing more plagioclase feldspar than orthoclase feldspar.
The term banatite is sometimes used informally for various rocks ranging from gr ...
or granite. Diorite also makes up some stocks intruded beneath large caldera
A caldera ( ) is a large cauldron-like hollow that forms shortly after the emptying of a magma chamber in a volcano eruption. When large volumes of magma are erupted over a short time, structural support for the rock above the magma chamber is ...
s.
Diorite source localities include Leicestershire and Aberdeenshire, UK; Thuringia
Thuringia (; german: Thüringen ), officially the Free State of Thuringia ( ), is a state of central Germany, covering , the sixth smallest of the sixteen German states. It has a population of about 2.1 million.
Erfurt is the capital and lar ...
and Saxony
Saxony (german: Sachsen ; Upper Saxon: ''Saggsn''; hsb, Sakska), officially the Free State of Saxony (german: Freistaat Sachsen, links=no ; Upper Saxon: ''Freischdaad Saggsn''; hsb, Swobodny stat Sakska, links=no), is a landlocked state of ...
in Germany; Finland; Romania; central Sweden; southern Vancouver Island
Vancouver Island is an island in the northeastern Pacific Ocean and part of the Canadian province of British Columbia. The island is in length, in width at its widest point, and in total area, while are of land. The island is the largest by ...
around Victoria
Victoria most commonly refers to:
* Victoria (Australia), a state of the Commonwealth of Australia
* Victoria, British Columbia, provincial capital of British Columbia, Canada
* Victoria (mythology), Roman goddess of Victory
* Victoria, Seychelle ...
, Canada; the Darran Range of New Zealand; the Andes Mountains; and Concordia in South Africa. Hornblende diorite is a common rock type in the Henry
Henry may refer to:
People
*Henry (given name)
* Henry (surname)
* Henry Lau, Canadian singer and musician who performs under the mononym Henry
Royalty
* Portuguese royalty
** King-Cardinal Henry, King of Portugal
** Henry, Count of Portugal, ...
, Abajo, and La Sal Mountains of Utah
Utah ( , ) is a state in the Mountain West subregion of the Western United States. Utah is a landlocked U.S. state bordered to its east by Colorado, to its northeast by Wyoming, to its north by Idaho, to its south by Arizona, and to it ...
, US, where it was emplaced as laccolith
A laccolith is a body of intrusive rock with a dome-shaped upper surface and a level base, fed by a conduit from below. A laccolith forms when magma (molten rock) rising through the Earth's crust begins to spread out horizontally, prying apar ...
s.
An orbicular variety found in Corsica was formerly called '' corsite''. An obsolete name for microdiorite, ''markfieldite'', was given by Frederick Henry Hatch in 1909 to exposures near the village of Markfield, England.
Use
Human use of diorite dates at least to the Middle Neolithic
The Neolithic period, or New Stone Age, is an Old World archaeological period and the final division of the Stone Age. It saw the Neolithic Revolution, a wide-ranging set of developments that appear to have arisen independently in several parts ...
, when it was used in a passage grave
A passage grave or passage tomb consists of one or more burial chambers covered in earth or with stone, and having a narrow access passage made of large stones. These structures usually date from the Neolithic Age, and are found largely in Wester ...
at Le Dolmen du Mont Ubé, Jersey
Jersey ( , ; nrf, Jèrri, label= Jèrriais ), officially the Bailiwick of Jersey (french: Bailliage de Jersey, links=no; Jèrriais: ), is an island country and self-governing Crown Dependency near the coast of north-west France. It is the l ...
. The use of stone of contrasting colour suggests that diorite was deliberately selected for its appearance.
The first great Mesopotamia
Mesopotamia ''Mesopotamíā''; ar, بِلَاد ٱلرَّافِدَيْن or ; syc, ܐܪܡ ܢܗܪ̈ܝܢ, or , ) is a historical region of Western Asia situated within the Tigris–Euphrates river system, in the northern part of the ...
n empire, the Akkadian Empire
The Akkadian Empire () was the first ancient empire of Mesopotamia after the long-lived civilization of Sumer. It was centered in the city of Akkad () and its surrounding region. The empire united Akkadian and Sumerian speakers under one ...
of Sargon of Akkad, began using diorite for sculpture after sources of the rock came under Akkadian control. Diorite was used to depict rulers or high officials in ceremonial poses or attitudes of prayer, and the sculptures may have been designed to receive funerary offerings. Diorite was also used for stone vases by Bronze Age
The Bronze Age is a historic period, lasting approximately from 3300 BC to 1200 BC, characterized by the use of bronze, the presence of writing in some areas, and other early features of urban civilization. The Bronze Age is the second prin ...
craftspeople, who developed considerable skill at polishing diorite and other stones. The Egyptians had become skilled at shaping diorite and other hard stones by 4000 BCE. A large diorite stela
A stele ( ),Anglicized plural steles ( ); Greek plural stelai ( ), from Greek , ''stēlē''. The Greek plural is written , ''stēlai'', but this is only rarely encountered in English. or occasionally stela (plural ''stelas'' or ''stelæ''), wh ...
in the Louvre Museum
The Louvre ( ), or the Louvre Museum ( ), is the world's most-visited museum, and an historic landmark in Paris, France. It is the home of some of the best-known works of art, including the ''Mona Lisa'' and the ''Venus de Milo''. A central l ...
dating to 1700 BCE is inscribed with the Code of Hammurabi.
Diorite was used by the Inca
The Inca Empire (also known as the Incan Empire and the Inka Empire), called ''Tawantinsuyu'' by its subjects, (Quechua for the "Realm of the Four Parts", "four parts together" ) was the largest empire in pre-Columbian America. The admin ...
civilization as structural stone. It was used by medieval Islamic builders to construct water fountains in the Crimea
Crimea, crh, Къырым, Qırım, grc, Κιμμερία / Ταυρική, translit=Kimmería / Taurikḗ ( ) is a peninsula in Ukraine, on the northern coast of the Black Sea, that has been occupied by Russia since 2014. It has a pop ...
. In later times, diorite was commonly used as cobblestone; today many diorite cobblestone streets can be found in England and Guernsey. Guernsey diorite was used in the steps of St Paul's Cathedral, London.
Today, diorite is uncommon in construction, although it shares similar physical properties with granite. Diorite is often sold commercially as "black granite". Diorite's modern uses include construction aggregate, curbing, usage as dimension stones, cobblestone, and facing stones.
File:Jar with Lug Handles LACMA M.71.73.54.jpg, Naqada II jar with lug handles; ; height: ; Los Angeles County Museum of Art
The Los Angeles County Museum of Art (LACMA) is an art museum located on Wilshire Boulevard in the Miracle Mile vicinity of Los Angeles. LACMA is on Museum Row, adjacent to the La Brea Tar Pits (George C. Page Museum).
LACMA was founded in 19 ...
(US)
File:Gudea of Lagash Girsu.jpg, '' Statue of Gudea I'', dedicated to the god Ningishzida
Ningishzida ( Sumerian: DNIN-G̃IŠ-ZID-DA, possible meaning "Lord f theGood Tree") was a Mesopotamian deity of vegetation, the underworld and sometimes war. He was commonly associated with snakes. Like Dumuzi, he was believed to spend a part ...
; 2120 BC (the Neo-Sumerian
The Third Dynasty of Ur, also called the Neo-Sumerian Empire, refers to a 22nd to 21st century BC (middle chronology) Sumerian ruling dynasty based in the city of Ur and a short-lived territorial-political state which some historians consider to ...
period); height: , width: , depth: ; Louvre
The Louvre ( ), or the Louvre Museum ( ), is the world's most-visited museum, and an historic landmark in Paris, France. It is the home of some of the best-known works of art, including the ''Mona Lisa'' and the ''Venus de Milo''. A central l ...
File:Weight Shulgi Louvre AO22187.jpg, Weight dedicated by King Shulgi with a crescent moon on it; 2094-2047 BC; weight: 248 g; Louvre
File:Head of a bearded god wearing a cap with horns dedicated by Puzur-Eshtar of Mari.jpg, Assyria
Assyria ( Neo-Assyrian cuneiform: , romanized: ''māt Aššur''; syc, ܐܬܘܪ, ʾāthor) was a major ancient Mesopotamian civilization which existed as a city-state at times controlling regional territories in the indigenous lands of the ...
n head of a bearded god wearing a cap with horns dedicated by Puzur-Eshtar of Mari; middle Bronze Age
The Bronze Age is a historic period, lasting approximately from 3300 BC to 1200 BC, characterized by the use of bronze, the presence of writing in some areas, and other early features of urban civilization. The Bronze Age is the second prin ...
; height: ; (Berlin
Berlin ( , ) is the capital and List of cities in Germany by population, largest city of Germany by both area and population. Its 3.7 million inhabitants make it the European Union's List of cities in the European Union by population within ci ...
, Germany)
File:Head of a Cow Goddess (Hathor or Mehetweret) MET DP311571.jpg, Head of a cow goddess (Hathor
Hathor ( egy, ḥwt-ḥr, lit=House of Horus, grc, Ἁθώρ , cop, ϩⲁⲑⲱⲣ, Meroitic: ) was a major goddess in ancient Egyptian religion who played a wide variety of roles. As a sky deity, she was the mother or consort of the sk ...
or Mehet-Weret
Mehet-Weret or Mehturt ( egy, mḥt-wrt) is an ancient Egyptian deity of the sky in ancient Egyptian religion. Her name means "Great Flood".
She was mentioned in the Pyramid Texts. In ancient Egyptian creation myths, she gives birth to the sun at ...
); 1390-1352 BC; height: , width: , depth: ; Metropolitan Museum of Art
The Metropolitan Museum of Art of New York City, colloquially "the Met", is the largest art museum in the Americas. Its permanent collection contains over two million works, divided among 17 curatorial departments. The main building at 1000 ...
(New York City)
File:Paris - Toutânkhamon, le Trésor du Pharaon - Amon protégeant Toutânkhamon - 005.jpg, Statue of Amun; 1336-1327 BC; height: , width: 44, length: ; Louvre
File:Block Statue of the God's Father Pameniuwedja, son of Nesmin and Nestefnut MET 07.228.25 EGDP023155.jpg, Block statue of the god's father Pameniuwedja, son of Nesmin and Nestefnut; 4th century BC; height: , width: , depth: ; Metropolitan Museum of Art
File:Pair of vases MET DT4387.jpg, Vase with gilt bronze ornaments; ; ; Metropolitan Museum of Art
File:Palazzo delle Poste di Napoli - ingresso.jpg, , Naples, Italy, Gino Franzi, 1936. Modernism
Modernism is both a philosophy, philosophical and arts movement that arose from broad transformations in Western world, Western society during the late 19th and early 20th centuries. The movement reflected a desire for the creation of new fo ...
, constructed with marble
Marble is a metamorphic rock composed of recrystallized carbonate minerals, most commonly calcite or dolomite. Marble is typically not foliated (layered), although there are exceptions. In geology, the term ''marble'' refers to metamorphose ...
and diorite.
See also
* List of rock types
References
External links
{{Authority control
Granitic rocks
Intermediate rocks
Plutonic rocks