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Lizardite is a mineral from the serpentine subgroup [3] with formula Mg 3 (Si 2 O 5)(OH) 4, and the most common type of mineral in the subgroup. [4] It is also a member of the kaolinite-serpentine group. [5] Lizardite may form a solid-solution series with the nickel-bearing népouite (pure end-member: Ni 3 (Si 2 O 5)(OH) 4).
Mohs hardness kit, containing one specimen of each mineral on the ten-point hardness scale The Mohs scale ( / m oʊ z / MOHZ ) of mineral hardness is a qualitative ordinal scale , from 1 to 10, characterizing scratch resistance of minerals through the ability of harder material to scratch softer material.
Serpentine subgroup (part of the kaolinite-serpentine group in the category of phyllosilicates) [1] are greenish, brownish, or spotted minerals commonly found in serpentinite. They are used as a source of magnesium and asbestos , and as decorative stone. [ 5 ]
Serpentine group minerals have a Mohs hardness of 2.5 to 3.5, so serpentinite is easily carved. [26] Grades of serpentinite higher in calcite, along with the verd antique (breccia form of serpentinite), have historically been used as decorative stones for their marble-like qualities.
The Mohs scale of mineral hardness; The Vickers hardness test; The Brinell scale; The Janka hardness test; The Rockwell scale; The Durometer scale; The Barcol scale;
Mohs's scale had two limitations: it was not linear, and most modern abrasives fall between 9 and 10.; [6] [7] so, later scientists attempted to increase resolution at the harder end of the scale. Raymond R. Ridgway, a research engineer at the Norton Company, modified the Mohs scale by giving garnet a hardness of 10 and diamond a hardness of 15.
The Mohs scale of mineral hardness, based on scratch hardness comparison, defines value 1 as the hardness of talc, the softest mineral. When scraped on a streak plate , talc produces a white streak, though this indicator is of little importance, because most silicate minerals produce a white streak.
On the Mohs hardness scale, pyrrhotite ranges from 3.5 to 4, [15] compared to 6 to 6.5 for pyrite. [16] Streak can be used when properties between pyrrhotite and other sulfide minerals are similar. Pyrrhotite displays a dark grey to black streak. [ 15 ]