Diorite

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diorite

[′dī·ə‚rīt]
(petrology)
A phaneritic plutonic rock with granular texture composed largely of plagioclase feldspar with smaller amounts of dark-colored minerals; used occasionally as ornamental and building stone. Also known as black granite.

Diorite

 

a magmatic rock composed of plagioclase (andesine or oligoclase), hornblende, and more rarely, augite and biotite; sometimes quartz is present. Chemically, diorite is characterized by an average amount of silicic acid (55-65 percent).

Several varieties of diorite may be distinguished: quartz, quartzless, hornblende, augite, and biotite. Its color is gray to greenish-gray, and its structure is characterized by clearly defined idiomorphic plagioclase, which distinguishes it from biotite and amphibole. Diorite is not widespread and as a rule is found with granites and granodiorites, more rarely with other rock; it appears as a local facies.,In addition diorite may form independent stocks, veins, laccoliths, and other intrusive massifs. It is used as a building material and in road building. Some varieties of diorite have many shades of color and lend themselves to polishing; these are used to face buildings and to make such articles as vases, table tops, and pedestals. In ancient Egypt and ancient Mesopotamia diorite was also used for sculpture. Hard, dense, and opaque, diorite is used as a general-purpose sculptural stone to create forms of severe structural design; it also used in fine graphic-linear cutting.


Diorite

 

magmatic rock of paleotype habit, similar to basalt chemically and in its mineral composition. Diorite is characterized by a relatively small silica content (45-52 percent). Its coloring is dark gray or greenish black. The dioritic (ophitic) structure is formed by randomly placed elongated small plagioclase crystals, with augite in the interstices. Diorite is especially distributed in regions with gently sloping stratification of the sedimentary rock that encloses it, as well as among volcanic lava and tufa. Diorites form shallow, congealed bodies (sills and dikes) whose depth varies from a few cm to 200 m or more. Diorite is used for road-building stone and for stone casting.

diorite

Medium- to coarse-grained rock composed essentially of plagioclase feldspar and ferromagnesium minerals.
References in periodicals archive ?
Drilling at Undaunted targeted previous intercepts from earlier in the year (see ASX release dated 01/03/11) and has identified a mineralised diorite with a strike length of 150m returning significant intercepts including: 16m @ 2.
These resistivity lows and discontinuities suggested that the diorite porphyry intrusion has been intensively mineralized and altered throughout these fracture areas.
At the head of Seldom Harbour irregularly layered gabbro and diorite grade to heterogeneous mafic rocks which contain enclaves of layered gabbro, some sharply bounded in metre-scale blocks, others apparently gradational to larger areas of massive gabbro.
This indicates the studied gabbroic-diorites are not comparable with stage-1 and stage-3 plutons however it can be comparable to some extent with stage-2 diorites of Petterson and Windley (1991).
For this purpose, bulk samples ( greater than 10kg each) from the various rocks, especially mineralized diorites, have been collected during field.
Sulfide mineralization occurs in association with diorites and quartz veins, along foliation planes, as dissemination and as supergene enrichment.
KAU is intruded by diorites, granitoids and trondjhemites of Thak intusive complex.
Mineralized, potassic altered diorite porphyry was intersected from 128 metres to 159 metres.
Results from the drilling program indicate that gold mineralization is widespread and associated with sulphide mineralization (pyrite) in sheared diorites and altered intermediate metavolcanics.
An earlier, four-hole, preliminary drill program at Northallerton carried out by Reunion intersected gold mineralization in sheared, altered diorites with auriferous quartz stringers.