Chamosite

Chamosite is the Fe 2+ end member of the chlorite group. A hydrous aluminium silicate of iron, which is produced in an environment of low-to-moderate-grade metamorphosed iron deposits, as grey or black crystals in oolitic iron ore. Like other chlorites, it is a product of the hydrothermal alteration of pyroxenes, amphiboles and biotite in igneous rock. The composition of chlorite is often related to that of the original igneous mineral, so that more Fe-rich chlorites are commonly found as replacements of the Fe-rich ferromagnesian minerals (Deer et al., 1992).

Chamosite is the Fe 2+ end member of the chlorite group. A hydrous aluminium silicate of iron, which is produced in an environment of low-to-moderate-grade metamorphosed iron deposits, as grey or black crystals in oolitic iron ore. Like other chlorites, it is a product of the hydrothermal alteration of pyroxenes, amphiboles and biotite in igneous rock. The composition of chlorite is often related to that of the original igneous mineral, so that more Fe-rich chlorites are commonly found as replacements of the Fe-rich ferromagnesian minerals (Deer et al., 1992). Chamosite has a laminar shape; sheets measure 20-200 μm (Rivas Sanchez et al., 2006). Chamosite may be greenish-grey or brown. The cleavage is length-slow; the orientation may be α ∧ c=small, β=b, γ ∧ α=small, optic plane= [0 10] (Heinrich, 1965) and has good cleavage on the {001} axis. It has a dull luster and greyish-green streak. Birefringence is much lower than that of the micas, illite, montmorillonite and vermiculite, and refractive indices are higher than those of kaolinite (Deer et al. 1992). The chamosite spectra show the reflection d=7.18 Å (principal value of the chlorite) and the reflection d=14.4 Å (which confirms the presence of chlorite) (Rivas Sanchez et al., 2006). https://webmineral.com/specimens/picshow.php?id=1654&target=Chamosite

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