CLINOCHLORE

Mg₅Al(Si₃Al)O₁₀(OH)₈
Monoclinic

Clinochlore, a magnesium aluminum silicate hydroxide mineral of the chlorite group, is found sparsely at both Franklin and Sterling Hill, and in the Franklin Marble.

Frondel and Ito (1975) reported, as pennine, pale rose-colored tiny crystals in a vug with sonolite in a veinlet cutting franklinite ore from Franklin. These crystals have a density of 2.74 g/cm³ and are biaxial, 2V = 0^o, with a = 1.586, and  b = g = 1.583; an analysis is given in Table 15. The “chlorite” reported and illustrated from the Buckwheat Dolomite by Peters et al. (1983) is likely clinochlore. Clinochlore is not uncommon in very small amounts, occurring as a vug-liner (Figure 22-27) or as isolated clusters of colorless or light green crystals. It occurs in the original baumite assemblage (Bailey and Guggenheim, 1989).

The writer has found clinochlore as tiny light brown pseudohexagonal crystals associated with kraisslite from Sterling Hill (#148911); the analysis is given in Table 15. Reilly (1983) reported a chlorite similar to Franklin chamosite (the brunsvigite of Frondel and Ito, 1975) from Sterling Hill drill-hole #124, 15 feet from its beginning on the 340 level. However, this material is not Fe-rich and thus not chamosite. It is a manganoan, zincian, ferroan chlorite, here referred to as clinochlore tentatively. The chemical composition is approximately (Mg_2.5Fe_1.0Mn_0.7 Zn_0.7)Al(Si₃Al)O₁₀(OH)₈.

Yau et al. (1984) reported chlorite replacing phlogopite in the Franklin Marble, and replacements of diopside may exist as well. Clinochlore is also found in other assemblages, commonly as a late-stage mineral in sparse amounts. However, these have not been studied.

Copyright © 1995 by Pete J. Dunn			Website by Herb Yeates
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