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, any of a group of widely distributed rock-forming minerals, magnesium-iron silicates, often with traces of calcium, aluminum, sodium, titanium, and other elements.
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(named for the Tremola Valley in the southern Swiss Alps), a monoclinic amphibole, Ca2Mg5[Si4O11](OH,F)2. Admixtures of Na, Fe, Mn, and Cr are regularly distributed in the octahedral positions of the structure, and admixtures of Al and P are located in the tetrahedral positions. The F~ and OH” content is correlated with the temperature of formation; tremo-lite with increased concentrations of F serves as a geologic thermometer for the characteristics of high-temperature geologic processes.
Tremolite forms grayish white acicular crystals and radiating columnar aggregates. Compact cryptocrystalline tremolite deposits are called nephrite, and silky fibrous aggregates form mountain leather or mountain cork. The hardness of tremolite on Mohs’ scale is 6–6.5, and its density is about 3,000 kg/m3.
Tremolite is a typical metamorphic mineral, formed in the early stage of contact metamorphosis of dolomites and lime stones. It is also characteristic of a low degree of regional metamorphism; it occurs less frequently in alpine-type veins and pegmatites. Deposits of mountain leather are located in Italy (Lombardy) and on Corsica.