Tremolite structure

This is because tremolite can be viewed as offset strips of talc strongly linked back-to-back by calciiun ions. A simple analogy would be to compare the tremolite structure to a brick wall, with the talc strips represented by the bricks and the calcium ions by the mortar. The structure is dense, rigid, and of high structural integrity. Talc, on the other hand, might be viewed as a stack of ceramic tiles. With litfle effort, one tile can be pushed across or removed from an adjacent tile in the stack. 

Figure 4.18 A clinographic view of the tremolite structure, a clinopyroxene. The ideal density for tremolite is 2.90 g/cc. 

Figure 5,35 Structure of tremolite projected on (001) plane. Dashed lines on [T40n] tetrahedral chains displacement (highly exaggerated for illustrative purposes) due to thermal decoupling. From Sueno et al. (1973). Reprinted with permission of The Mineralogi-cal Society of America.

Hawthorne F. C. and Grundy H. D. (1976). The crystal chemistry of the amphiboles, IV X-ray and neutron refinement of the crystal structure of tremolite. Canadian Mineral, 14 334-345. 

The Arnold Pit is on the steeply dipping, overturned limb of the Sylvia Lake Syncline, the structural hanging wall is the stratigraphic footwall. Commercial talc occurs in Unit 13 near the contact with Unit 14 of the Upper Marble from the metamorphism or impure evaporative dolomite. The upper section of Unit 13 grades from tremolite-rich talc ore into a pure talc schist up section. Unit 12 is a white massive doiomitic marble with convolute bands of grey and orange to... 

Actinolite-tremolite is another mineral series whose names are well-known because of their fibrous habit. Tremolite, the magnesium end member of the series is depicted in Fig. LIE. Other minerals of similar structure but containing iron as well as magnesium were called actinolite. Ferroactinolite, is the name of the ideal 100% iron (Fe) end member. An accurate designation of the series is... 

Crystal Structure of Tremolite [NaCa2Mg5(Si7A1022)(OH)2] and Paragasite, [NaCa2Mg4Al(Si6Al2022)(0H,F)2]... 

Paragasite, NaCa2Mg4Al(Si6Al2022)(0H,F)2, has the same structure as tremolite with A1 replacing one Mg and another A1 atom for charge balance. Some OH- is replaced by F. The notation is the same except an A1 atom replaces one Mg atom. Tremolite and paragasite are asbestos minerals. 

In the double chains or ribbons, there are different kinds of tetrahedra sharing two and three vertices. The most numerous amphiboles and asbestos minerals, such as tremolite, Ca2Mgs(Si40n)2(0H)2, adopt the [Si40n] 6 doublechain structure, as shown in Fig. 14.4.9(f). 

A typical amphibole is tremolite, Ca2Mg5(Si4On)2(OH)2. Although it would not seem to be absolutely necessary, amphiboles apparently always contain some hydroxyl groups attached to the cations. Aside from this, however, they are structurally similar to the pyroxenes, in that the (SLOnjn bands lie parallel and are held together by the metal ions lying between them. Like the pyroxenes and for the same reason, they are subject to some variability in the particular cations incorporated. 

Tremolite and actinolite form a continuous mineral series in which Mg and Fe(ll) can freely substitute with each other while retaining the same three-dimensional crystal structure. Tremolite has little or no iron while actinolite contains iron (Jolicoeur et al. 1992 Ross 1981 Skinner et al. 1988). 

The Fibrous Minerals. The fibrous minerals contain very long silicate ions in the form of tetrahedra condensed into a chain, as shown in Figure 31-6. These crystals can be cleaved readily in directions parallel to the silicate chains, but not in the directions which cut the chains. Accordingly crystals of these minerals show the extraordinary property of being easily unravelled into fibers. The principal minerals of this sort, tremolite, C.a.jMg..Si 022(0H)2, and chrysotile, Mg6Si40u(0H)p/H20, are called asbestos. Deposits of these minerals are found, especially in South Africa, in layers several inches thick. These minerals are shredded into fibers, which are then spun or felted into asbestos yarn, fabric, and board for use for thermal insulation and as si heat-resistant structural material. 

The composition of talc varies depending on its source. The most important factor is the amount of tremolite present. In the USA, for instance, Montana talcs are considered to be asbestos and tremolite free. The California plate-like talcs contain minor amounts of tremolite (less than 3%), whereas hard talcs contain between 5 to 25% tremolite. Some industrial talcs mined in upper New York State contain 25 to 50% tremolite. The other important component in its composition is water which is chemically combined in the magnesium oxide or brucite layer. Figure 2.62 shows the molecular structure of talc. Talc may lose this water only on... 

The term asbestos is usually applied to a fibrous group of minerals that includes the amphiboles, such as tremolite, Ca2(OH)2Mg5(S 14011)2, with double-chain structures, and chrysotile, Mg3(0H)4Si205. In chrysotile, the dimensions of the silicate and magnesium layers are different, resulting in a curling that forms the characteristic cylindrical fibers. 

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