Fe-tremolite

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... 

Riebeckite (variety crocidolite)—Na2(Fe, Mg)3Fe Anthophyllite—Mg7Sig022(OH)2 Tremolite—Ca2Mg5Sig022(OH)2 Actinolite—Ca2(Mg,Fe )5Sig022(OH)2... 

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). 

Actinolite— A mineral in the amphibole group, a calcium magnesium (iron) silicate with the chemical formula Ca2(Mg,Fe)5Sig022(0H)2. The mineral occurs as a series in which magnesium and iron can freely substitute for each other. Actinolite is the intermediate member when iron is predominant the mineral is ferro-actinolite and when magnesium is predominant, the mineral is tremolite. The iron produces a green color that darkens as the iron content increases. Actinolite may occur in fibrous form (an asbestos). It is not used commercially, but is a common impurity in chrysotile asbestos. 

Thus, water can be stored in silicates and liberated by heating of hydrated silicates. This group of metamorphic rocks includes serpentine (Mg,Fe)3Si205 (OH)4 and tremolite Ca2Mg5Si8022 (OH)2. Serpentine, a basic orthosilicate, is a very common secondary mineral, resulting from a hot water alteration of magnesium silicates (mostly peridotite), present in magma, a process termed serpentinization ... 

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. 

Double chain structures are observed in certain minerals. In these cases two simple chains are cross-linked by sharing oxygen atoms. The basic unit is (Si Ojj). Adjacent double chains are joined by the metal cations. The resulting structure is mechanically very strong in direction of orientation of anions it is weak in the perpendicular direction. A fibrous nature is thus imparted to the mineral. This type of structure exist in a class of minerals called amphiboles like tremolite CajMg5(Si O )j(OH)y amocite QAg, Fe), (Si, (OH). ... 

---