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 (~50¼ 03Õ 42.95Ó North, ~94¼ 18Õ 55Ó 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. ItÕs
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
PentagonÕs 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
IndiaÕs Andhra Pradesh State. It is very similar to the ÒTan Brown GraniteÓ
shown above. This ÒSapphire Brown GraniteÓ 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. ÒRosa Beta GraniteÓ above). ÒLuna Pearl GraniteÓ has potassium
feldspar, sodic plagioclase feldspar, quartz, amphibole, and biotite
mica. The term ÒleucograniteÓ 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 Mem—ria Stock, a post-Pan-African Orogeny intrusion in the Santa QuitŽria Granitic-Migmatitic Complex, Central Cear‡ Domain, Middle Ordovician (a correlative stock dates to 466 Ma).
Locality: commercial quarry on northwestern side of Fazenda Mem—ria (hill), NNW of Santa QuitŽria, northern Cear‡ State, northeastern Brazil (04¼ 11Õ 27.78Ó South, 40¼ 13Õ 27.60Ó West).