KENTROLITE Chapter16. Sorosilicates and cyclosilicates

KENTROLITE

Pb₂Mn³⁺₂Si₂O₉
Orthorhombic




	Figure 16-13. Prismatic crystal of kentrolite from Franklin. Field of view is 0.2 mm in maximum dimension.

Kentrolite, a lead manganese silicate mineral, was reported by Palache (1935) on the basis of morphological examination only. No specimens were preserved or found for over 50 years. It was found again by the writer in 1986, associated with groutite, cahnite, hetaerolite, and calcite in a brown andradite matrix (Figure 16-13); this is the more common of the two assemblages for Franklin groutite (Dunn, 1987). It was verified using X-ray powder-diffraction methods, and a semi-quantitative analysis showed only Mn, Pb, and Si as constituents.




	Figure 16-14. Crystals of kentrolite from Franklin, showing subparallel growth. Field of view is 0.3 mm in maximum dimension. Photo courtesy of Herb Yeates.

Another assemblage, consisting of spicular crystals of kentrolite associated with barysilite and willemite from Franklin, was described and illustrated by Yeates (1991), who found it to have end-member composition. Later in 1991 another possibly different assemblage of deep-red crystals of kentrolite associated with manganaxinite, cahnite, and datolite was noted by Cianciulli (1991b) (Figure 16-14). Because Palache (1935) did not mention these distinct assemblages, a different kentrolite-bearing assemblage may have been known to him.

FOOTER LBI




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