Metamorphic Rocks
METAMORPHIC ROCKS were formed by the recrystalization of sedimentary or magmatic rocks under the earth's surface during raised pressure and temperature conditions, from low to high grade metamorphism.(Commercial slates are metamorphic rocks exposed to low metamorphism. High metamorphic rocks such as gneisses belong to commercial granites.)
Gneiss group contains rocks with high pressure and high temperature metamorphism, which have strongly oriented, schlieren, banded, and wavy structures such as paragneisses, orthogneisses, garnet gneisses, migmatites and granulites. Migmatites and granulites are added to gneiss group only because of their similar structures.
- Paragneisses were formed by strong metamorphism of clayey sedimentary rocks (slates, clayey sandstones).
- Orthogneisses were created by strong metamorphism of light magmatic rocks (granite group, light volcanics).
- Garnet gneisses are rich in garnet & can be formed like para- or ortho-gneisses.
- Migmatites were formed by partial melting of gneisses.
- Granulites were created by very strong metamorphism of light magmatic rocks.
Metaconglomerates are formed by metamorphism of conglomerates - sedimentary rocks composed of rounded grains over 2 mm (4 mm in Europe).
(Quartzites are almost exclusively composed of quartz, metamorphosed from quartz sandstones. They are sometimes separated as an individual commercial stone group.)
GEOLOGICAL AGE
The age of the stone is determined in this table by the geological time unit when the stone was created by the geological process. In some cases the older the stone the greater the strength and lesser the water absorption is characteristic.
The basic geological periods with their ages are:
Quaternary (0 - 2 million years)
Terciery
Neogene (2 - 25 million years)
Paleogene (25 - 65 million years)
Mesozoic
Cretaceous (65 - 135 million years)
Jurassic (135 - 205 million years)
Triassic (205 - 250 million years)
Paleozoic
Permian (250 - 295 million years)
Carboniferous (295 - 355 million years)
Devonian (355 - 415 million years)
Silurian (415 - 440 million years)
Ordovician (440 - 495 million years)
Cambrian (495 - 540 million years)
Proterozoic (540 - 2500 million years)
Archean (2500 - 4550 million years)
More resources:
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Marble Coffee Tables
Natural Stone is turning up more and more often in combination with furniture, e.g. in the kitchen surface, in wash basins, bathrooms, or coffee tables.
Bathrooms New Jersey
Granite lends itself to a variety of locations in traditional and modern houses for hallways,stairways, living areas, bathrooms and particularly, work surfaces such as kitchen tops and vanity tops.