Geology Wiki



Diorite classification on QAPF diagram

Quartzite is a type of rock. It forms when sandstone is changed by high temperature and pressure. Quartzite is used to make floors, roofs, and kitchen counters in some parts of the world. By Luna

Rock type Igneous rock
Essential mineral(s) plagioclase feldspar (typically andesine), biotite, hornblende, pyroxene, quartz, microcline, and olivine.
Accessory mineral(s) Zircon, apatite, sphene, magnetite, ilmenite, and sulfides
Similar rock(s) Quartz diorite

Diorite is a grey to a 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 and 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 cordilleran mountain buildings such as large batholiths in the Andes Mountains. The extrusive volcanic equivalent rock type is andesite.



Diorite is a relatively rare rock; source localities include Leicestershire; UK (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; Minnesota in the USA, and Idahet in Egypt.

An orbicular variety found in Corsica is called corsite.

Historic use[]

Diorite is a tough 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. However, its hardness also allows it to be worked finely and take a high polish and 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 2.23 m (7 ft 4 in) pillar of black diorite. The original can be seen today in Paris' Musée du Louvre.[1] The use of diorite in art was most significant 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, 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[]


Template:Igneous rocks