Currently, the American Society for Testing and Materials divides natural facing stone into six categories: Granite, Limestone, Marble, Quartz-based, Slate and other stone.
1. Granite (Granite)
Definition: Granular igneous rock, usually from pink to light gray or dark gray, mainly composed of quartz and feldspar, accompanied by a small amount of black minerals, uniform grain texture, and some gneiss or porphyry structures.
Limestone (Limestone)
Definition: A sedimentary rock consisting mainly of calcium carbonate (calcite mineral) or calcium magnesium carbonate (baiyun mineral), or a mixture of two minerals, commercially available as follows: limestone, shell limestone, dolomite , microcrystalline limestone, braided limestone, recrystallized limestone, tuff.
Performance classification:
Low density limestone with a density in the range of 1.76-2.16g/cm3.
Medium density limestone with a density in the range of 1.76-2.56 g/cm3.
High-density limestone with a density above 2.56g/cm3
Three. Marble (Marble)
Definition: This type of stone must be able to be polished, with a wide variety of composition and structure types, ranging from pure carbonates to rocks with very low carbonate content, which are collectively referred to as marble. Most of them have patterns or veins, and the crystal grain size ranges from cryptocrystalline to 5 mm in diameter.
classification:
Commercially divided into calcite marble, dolomite marble, agate striped marble, serpentine marble, tuff marble and so on.
Calcite marble: mainly composed of calcite, which forms a unique crystal structure due to recrystallization.
Dolomite marble: mainly composed of dolomite, which forms a crystal structure after high temperature and high pressure during metamorphism.
Serpentine marble: mainly composed of serpentine (magnesium silicate hydrate), green or dark green, accompanied by dolomite, calcite or magnesite.
Tuff marble: a porous, water-permeable layer structure containing some calcite crystals.
4. Sandstone (Quartz-based)
Definition: A type of sedimentary rock consisting mainly of mineral and rock particles (particle size 0.06-2 mm) and containing more than 60% silica. It has a multi-voided structure formed by the condensation of silica, iron oxide, carbonate or clay.
classification:
Commercially divided into blue-grey sandstone, brown sandstone, orthorhombic sandstone, quartzite, gravel, siltstone.
Sandstone: The silica content is 60-90%.
Normal quartz: The silica content is between 90 and 95%.
Quartzite: The silica content is above 95%.
V. Slate
Definition: It belongs to microcrystalline metamorphic rocks, usually derived from shale, mainly composed of mica, oxynitride and quartz. The slate contains mica minerals with an approximately parallel orientation that can be split along the bedding plane to form thin, hard slabs.
Other stone
Some stones of the sub-gem grade, such as jade, are sometimes used as facing stone. The general dosage is not very large, and the starting point is affixed. Others include alabaster, greenstone, schist, soapstone and more.
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