GRANITES  &  PORPHYRITIC  GRANITES

 

True granites (= monzogranites & syenogranites & porphyritic varieties) make up most of the commercial granite trade.  Countless varieties are quarried around the world.

 


 

Pink Westerly Granite - a fairly typical granite with an even phaneritic texture.  This rock comes from near Westerly in southwestern Rhode Island, USA.  It is mid-Early Permian in age, dating to 279 million years (= Sakmarian Stage or Artinskian Stage, depending on what geologic time scale one uses).

 


 

Salisbury Pink Granite - pinkish monzogranite (formerly referred to as adamellite) from near Salisbury, west-central North Carolina, USA.  This rock is quarried from the Early Devonian (411 million years) Salisbury Pluton.  It is dominated by quartz, K-feldspar, and plagioclase feldspar.  The unit also contains whitish-colored monzogranites, but the pink variety is valued more as a decorative stone.

 


 

Crystal Gold Granite - porphyritic granite with quartz, K-feldspar, plagioclase feldspar, and mafic mineral(s) from an English River Subprovince intrusion (Neoarchean, 2.66-2.71 Ga).  This rock comes from the Second Mountain Quarry, ~3 to 4 km east of Forgotten Lake, north of Redditt, north of the Trans-Canada Highway, NNE of Kenora, western Ontario, southern Canada (~50ľ 03’ 42.95” North, ~94ľ 18’ 55” West).

 


 

Dakota Mahogany Granite - porphyritic granite from the Milbank Granite (late Neoarchean, 2.6-2.7 billion years).  It is quarried just east of Milbank, in northeastern Grant County, northeastern South Dakota, USA.  The large brownish-salmon colored crystals are potassium feldspar (K-feldspar) (KAlSi3O8 - potassium aluminosilicate).  The bluish-gray, glassy-looking crystals are quartz (SiO2 - silica).  The black crystals are ferromagnesian mineral(s).

 


 

Columbia Pink Granite - a scarce decorative stone variety from New Hampshire.  It comes from a now-inactive quarry near Meriden Hill, 2 miles east of Tinkerville in western Coos County, northern New Hampshire.  It’s an attractive porphyritic granite with quartz (gray), K-feldspar (pink), sodic plagioclase feldspar (whitish), and biotite mica (black).  This rock comes from the Jurassic-aged Conway Granite (White Mountain Plutonic Series).

Columbia Pink Granite is no longer quarried.  Recently, however, material was specially obtained & used to replace the Pentagon’s entrance steps that were destroyed by the 9/11/2001 terrorist attacks in Washington D.C.  The original steps were composed of Swenson Pink Granite from Maine, which is no longer available.  Columbia Pink Granite was considered to be a close match.

Some info. provided by Bob Pope (president of Swenson Granite Company) & Dorothy Richter (former geologist with Rock of Ages granite company).

 


 

Carioca Gold Granite - a yellowish, Neoproterozoic to Cambrian (~650-500 million years) porphyritic granite from Lavras in Rio de Janeiro State, southeastern Brazil.  The rock has creamy-yellowish & yellowish-brown crystals of K-feldspar, grayish crystals of quartz.  The black crystals are hornblende amphibole.

 


 

Antique Yellow Granite - a yellowish, Neoproterozoic-Cambrian (~650-500 million years) granite from Espirito Santo State, near the southeastern coast of Brazil.  It has K-feldspar (yellowish & brownish), quartz (grayish), and biotite mica (black).

 


 

 

Violetta Granite - a Neoproterozoic to Cambrian (~650-530 million years) granite from Najran in the far-southern Arabian Shield of Arabia.  It is distinctive in having dark reddish-violet colored fractures in the potassium feldspar component (large light pinkish crystals).  The glassy-grayish and bluish-gray crystals are quartz, and the black crystals are hornblende amphibole.

 


 

Tropical Brown Granite - another Neoproterozoic-Cambrian (~650-530 million years) granite from the southern Arabian Shield.  It has large crystals of K-feldspar (brownish), quartz (dark brownish-gray), and hornblende amphibole (black).

 


 

Tan Brown Granite - an Archean porphyritic granite from Andhra Pradesh State in southern India.  This is one of a large number igneous & metamorphic decorative stones produced in India.  Many come from the Eastern Ghats Orogenic Belt, an ancient mountain belt running along the eastern margin of Peninsula India.  This rock is distinctive in having bluish-gray quartz crystals and large brownish-salmon colored K-feldspar crystals with obvious internal exsolution lamellae and internal disruptions.

 


 

Sapphire Brown Granite - another Archean porphyritic granite from southern India’s Andhra Pradesh State.  It is very similar to the “Tan Brown Granite” shown above.  This “Sapphire Brown Granite” has a larger bluish-gray quartz component in comparison.

 


 

Rosa Beta Granite - a quite attractive porphyritic monzogranite from the Sardinian-Corsican Batholith of Sardinia.  It dates to the Late Pennsylvanian-Early Permian, at ~280-310 million years.  This material is quarried at Luogosanto in northern Sardinia, a large island in the Mediterranean, west of Italy.  The large pinkish crystals are potassium feldspar.  The whitish crystals are sodic plagioclase feldspar.  The grayish crystals are quartz.  The black crystals are hornblende amphibole & biotite mica.

 


 

Luna Pearl Granite - a subporphyritic biotite leucogranite, also derived from the Late Pennsylvanian-Early Permian Sardinian-Corsican Batholith (cf. “Rosa Beta Granite” above).  “Luna Pearl Granite” has potassium feldspar, sodic plagioclase feldspar, quartz, amphibole, and biotite mica.  The term “leucogranite” refers to especially pale or whitish-colored granites.  The prefix leuco- has been applied to other rocks as well (see info. on a brecciated leucogabbro from the Moon).

 


 

Giallo Napoleone Granite - porphyritic alkaline granite from the late Neoproterozoic to Cambrian of Espirito Santo State, southeastern Brazil.

 


 

Alaskan White Granite - a porphyritic garnetiferous leucogranite with plagioclase feldspar, quartz, mica, potassium feldspar, and garnet from the Ordovician of Brazil.

Geologic Unit & Age: Fazenda Memória Stock, a post-Pan-African Orogeny intrusion in the Santa Quitéria Granitic-Migmatitic Complex, Central Ceará Domain, Middle Ordovician (a correlative stock dates to 466 Ma).

Locality: commercial quarry on northwestern side of Fazenda Memória (hill), NNW of Santa Quitéria, northern Ceará State, northeastern Brazil (04ľ 11’ 27.78” South, 40ľ 13’ 27.60” West).

 


 

 

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