Because the minerals are mostly fine-grained, it is much more difficult to distinguish between the different types of extrusive igneous rocks than between different types of intrusive igneous rocks.
22.
The Ortiz Mountains are part of the larger Ortiz porphyry belt of Santa Fe County, and consist of late Eocene to early Oligocene intrusive igneous rocks and their sedimentary host rock.
23.
The Silurian tableland in the northwest of the county is pierced by intrusive igneous rocks in the form of dikes and bosses, which are regarded as of Lower Old Red Sandstone age.
24.
"' Granodiorite "'( ) } } } } is a phaneritic-textured intrusive igneous rock similar to granite, but containing more plagioclase feldspar than orthoclase feldspar.
25.
If crystallization occurs at the Earth�s surface, extrusive igneous rocks are formed; if crystallization occurs within the Earth�s lithosphere, intrusive igneous rocks are formed which can then be brought to Earth�s surface by denudation.
26.
"' Anorthosite "'( ) is a phaneritic, intrusive igneous rock characterized by a predominance of plagioclase feldspar ( 90 100 % ), and a minimal mafic component ( 0 10 % ).
27.
They are primarily made up of quartz veins also known as lodes or " reefs ", which contain either native gold or gold sulfides and faults, they may occupy intrusive igneous rocks such as granite.
28.
Can�vanas combines flat alluvial plains in the center and north, areas with both gentle hills and rugged, deeply dissected mountainous areas made up of volcaniclastic rocks ( lava flows and exposed intrusive igneous rocks ) to the southeast and south.
29.
Coarse-grained intrusive igneous rocks that form at depth within the earth are called abyssal while those that form near the surface are called foliation of the country rock : if the intrusion is parallel the body is concordant, otherwise it is discordant.
