Double silicate chains

Double-chain silicates. Double-chain silicates, (Si40n)n6n, are known as amphiboles, such as tremolite, Ca2Mg5(0H)2[(Si40n)2]. These include the true asbestoses, such as crocidolite or blue asbestos,... 

Pyroxenes e.g., Mg2[Si2Ofi] = 2MgSi03, enstatite) and amphiboles (double chain silicates containing OH groups) form chains of Si04 tetrahedra. By interlinking the chains we arrive at layer silicates. 

In solids of known composition containing more than one type of Q unit, separate lines were observed in the requisite intensity ratio. For instance, the spectrum of xonotlite, Ca6(OH)2(Si6Ol7), a double-chain silicate branched at every third silicon,... 

Two molecular types of silicates are referred to as asbestos. Chrysotile is a magnesium silicate built upon a layered structure of silicate rings and Mg(OH)2. The layered structure causes the sheets to roll into cylinders approximately 200A in diameter. Amphibole asbestos may contain a variety of cations but is built upon a double chain silicate structure. The chrysotile asbestos is always found as an asbestiform crystal while the amphiboles may be either acicular or asbestiform. 

Fig. 5.18. The Si L2 3 x-ray emission spectra of various silicates, as shown, and of quartz. In terms of structural silicate groups (1-7) are island silicates, (8-9) ring silicates, (10-U) single-chain silicates, (12-15) double-chain silicates, (16-19) sheet silicatesj (20-22) framework silicates (after Dikov et al., 1976 reproduced with the publisher s permission).

Fig. 3. Silicate backbones of chrysotile and amphiboles (a) the sheet silicate structure of chrysotile, analogous to that of micas (b) the double-chain silicate...

Subclass Inosilicate - Double Chain In the double chain inosilicates, two parallel chains are linked together by their alternate tetrahedra. The basic structural group is Si40if . The amphibole group of minerals are double chain silicates, for example the tremolite-ferroactinolite series -Ca2(Mg,Fe)5Sig022(OH)3. 

Fig. 6.8. Examples of linear double-chain silicate stmctures...

Double-chain silicates, shown in Figure I5.13f, find some SiO units sharing two oxygens while others share three. The repeating unit is Si40if. Five double-chain silicates [tremolite, anthophyllite, actinolite, amosite ( brown asbestos ), crocidolite ( blue asbestos ), all members of the amphibole family of minerals] and the serpentine mineral chrysotile ( white asbestos ) are classified under the generic name asbestos. The molecular-level chain structure of these materials is reflected in... 

Sihcon—oxygen bonds dominate the chemistry of the silicates, silica, and the aluminosihcates.The SiO unit can be linked together to form rings, chains, sheets, and three-dimensional arrays. Asbestos is a generic name for a class of double-chain silicates that, until lately, has been put to a wide variety of uses. SiHca comes in a variety of polymorphs including the optically active a-quartz. Quartz is also piezoelectric. Water glass and siUca gel have a variety of practical appHcations. When aluminum replaces some silicon atoms in a silicate, the aluminosilicates result. These include the zeolites and the micas. 

Associate an important, practical mineral with each of the following types of silicates (a) orthosilicate, (l>) single-chain silicate, (double-chain silicate,... 

Clinoamphiboles are monoclinic (C2/m) hydrous double-chain silicates that are common in metamorphic rocks. Dislocation structures have been studied in hornblende ((Ca, Na, K)2 3(Mg, Fe, Al)5(OH, F)2(Si, Al)2Si6022) and glaucophane (Na2Mg3Al2(0HT )2Si8022). 

---