Diorite


Diorite
Diorite
Diorite classification on QAPF diagram

Diorite (play /ˈdaɪərt/) is a grey to dark grey intermediate intrusive igneous rock composed principally of plagioclase feldspar (typically andesine), biotite, hornblende, and/or pyroxene. It may contain small amounts of quartz, microcline and olivine. Zircon, apatite, sphene, magnetite, ilmenite and sulfides occur as accessory minerals.[1] It can also be black or bluish-grey, and frequently has a greenish cast. Varieties deficient in hornblende and other dark minerals are called leucodiorite. When olivine and more iron-rich augite are present, the rock grades into ferrodiorite, which is transitional to gabbro. The presence of significant quartz makes the rock type quartz-diorite (>5% quartz) or tonalite (>20% quartz), and if orthoclase (potassium feldspar) is present at greater than ten percent the rock type grades into monzodiorite or granodiorite. Diorite has a medium grain size texture, occasionally with porphyry.

Diorites may be associated with either granite or gabbro intrusions, into which they may subtly merge. Diorite results from partial melting of a mafic rock above a subduction zone. It is commonly produced in volcanic arcs, and in cordilleran mountain building such as in the Andes Mountains as large batholiths. The extrusive volcanic equivalent rock type is andesite.

Contents

Occurrence

Diorite

Diorite is a relatively rare rock; source localities include Leicestershire; UK[2] (one name for microdiorite - Markfieldite - exists due to the rock being found in the village of Markfield), Sondrio, Italy; Thuringia and Saxony in Germany; Finland; Romania; Northeastern Turkey; central Sweden; Scotland; the Darrans range of New Zealand; the Andes Mountains; the Isle of Guernsey; Basin and Range province and Minnesota in the USA; Idahet in Egypt

An orbicular variety found in Corsica is called corsite.

Historic use

Diorite Porphyry vase from predynastic Ancient Egypt, ca. 3600 BC; approx 30 cm.

Diorite is an extremely hard rock, making it difficult to carve and work with. It is so hard that ancient civilizations (such as Ancient Egypt) used diorite balls to work granite. Its hardness, however, also allows it to be worked finely and take a high polish, and to provide a durable finished work.

One comparatively frequent use of diorite was for inscription, as it is easier to carve in relief than in three-dimensional statuary. Perhaps the most famous diorite work extant is the Code of Hammurabi, inscribed upon a 2.23m (7ft 4in) pillar of black diorite. The original can be seen today in Paris' Musée du Louvre.[3] The use of diorite in art was most important among very early Middle Eastern civilizations such as Ancient Egypt, Babylonia, Assyria and Sumer. It was so valued in early times that the first great Mesopotamian empire -- the Empire of Sargon of Akkad -- listed the taking of diorite as a purpose of military expeditions.

Although one can find diorite art from later periods, it became more popular as a structural stone and was frequently used as pavement due to its durability. Diorite was used by both the Inca and Mayan civilizations, but mostly for fortress walls, weaponry, etc. It was especially popular with medieval Islamic builders. In later times, diorite was commonly used as cobblestone; today many diorite cobblestone streets can be found in England, Guernsey and Scotland, and scattered throughout the world in such places as Ecuador and China. Although diorite is rough-textured in nature, its ability to take a polish can be seen in the diorite steps of St. Paul's Cathedral, London, where centuries of foot traffic have polished the steps to a sheen.

See also

References

  1. ^ Blatt, Harvey and Robert J. Tracy (1996) Petrology, W. H. Freeman, 2nd edition, p. 53 ISBN 0-7167-2438-3
  2. ^ Midland Quarry Products
  3. ^ The Louvre: Law Code of Hammurabi

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Look at other dictionaries:

  • diorite — [ djɔrit ] n. f. • 1817; du gr. diorizein « distinguer » ♦ Géol. Roche éruptive grenue, formée de cristaux de feldspath (couleur blanche) et d amphibole (couleur verte). ● diorite nom féminin (grec dioridzein, distinguer) Roche plutonique… …   Encyclopédie Universelle

  • Diorite — Di o*rite, n. [Cf. F. diorite. See {Diorism}.] (Min.) An igneous, crystalline in structure, consisting essentially of a triclinic feldspar and hornblende. It includes part of what was called greenstone. [1913 Webster] …   The Collaborative International Dictionary of English

  • diorite — s. f. [Geologia] Espécie de rocha ígnea composta de feldspato e anfíbola. = DIORITO   ‣ Etimologia: francês diorite …   Dicionário da Língua Portuguesa

  • diorite — [dī′ə rīt΄] n. [Fr < Gr diorizein, to divide < dia , through + horizein, to separate: see HORIZON] a dark gray, intrusive igneous rock consisting chiefly of plagioclase and hornblende …   English World dictionary

  • Diorite — Hache polie en diorite néolithique – Environs de Reims (Marnes) France – Collection d’Alexis Damour – Muséum de Toulouse PRE.2009.0.215.1 (250x52x33mm) La diorite est une roche magmatique plutonique grenue composée de plagioclase, d amphibole …   Wikipédia en Français

  • diorite — dioritic /duy euh rit ik/, adj. /duy euh ruyt /, n. a granular igneous rock consisting essentially of plagioclase feldspar and hornblende. [1820 30; < F < Gk dior(ízein) to distinguish (see DI 3, HORIZON) + F ite ITE1] * * * Medium to coarse… …   Universalium

  • diorite — (di o ri t ) s. m. Terme de minéralogie. Roche nommée Grünstein par les Allemands, qui se compose essentiellement de feldspath et d amphibolite, et qui passe souvent à une masse homogène. Le diorite porte aussi le nom de diabase. ÉTYMOLOGIE… …   Dictionnaire de la Langue Française d'Émile Littré

  • diorite — di·o·rì·te s.f. TS petr. roccia eruttiva plutonica a struttura granulare con prevalenza di plagioclasi associati a pirosseni, anfiboli o biotite {{line}} {{/line}} DATA: 1817. ETIMO: dal fr. diorite, 1817, der. del gr. diorízō distinguo …   Dizionario italiano

  • diorite — dioritas statusas T sritis chemija apibrėžtis Vidutinio rūgštingumo magminė intruzinė uoliena. atitikmenys: angl. diorite rus. диорит …   Chemijos terminų aiškinamasis žodynas

  • diorite — noun Etymology: French, irregular from Greek diorizein to distinguish, from dia + horizein to define more at horizon Date: 1826 a granular crystalline igneous rock commonly of acid plagioclase and hornblende, pyroxene, or biotite • …   New Collegiate Dictionary


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