SCLARITE

(Zn,Mg,Mn)₄Zn₃(CO₃)₂(OH)₁₀ 
Monoclinic, A2/a, a = 16.110, b = 5.432, c = 15.041 Å,
b = 95.49^o, Z = 4

Sclarite was first described from Franklin by Grice and Dunn (1989); it remains unique to the deposit.

Crystal structure

Sclarite is isostructural with loseyite (Hill, 1980; Grice and Dunn, 1989) and has Zn atoms occupying both octahedral and tetrahedral sites.

Description

Sclarite occurs as colorless transparent l.5 mm crystals which form slightly divergent arrays; such clusters can resemble very coarse-surfaced spherules and are grayish white in the aggregate. Individual sclarite crystals are prismatic, elongate on [010], and tabular on [001]; a minor {100} pinacoid is present. The luster is vitreous; no cleavage was observed; and the density is 3.51 g/cm³.

Optically, sclarite is biaxial, positive, 2V = 63.4^o, with a = 1.648, b = 1.664, and g = 1.702. Dispersion is strong, r >> v; the orientation is Y = b, X L c = 49^o; and there is no discernible response to ultraviolet.

Composition

Sclarite is a zinc carbonate hydroxide mineral and the zinc analogue of loseyite. Analysis by Grice and Dunn (1989), with H₂O and CO₂ calculated, yielded FeO 0.1, MgO 6.7, MnO 4.2, ZnO 62.0, CO₂ [12.67], H₂O [12.97], total = 98.6 wt. %.

Occurrence and paragenesis

Sclarite is known on but one specimen from Franklin and has not been found at Sterling Hill. It occurs on calcite-free, granular, willemite-franklinite  ore; the specimen is slightly sheared and has minor zincite present. The exposed surface is coated unevenly with sparse leucophoenicite, dense abundant gageite, and sparse secondary zincite. These species are coated with rhodochrosite spherules, chlorophoenicite, and additional gageite. Sclarite is among the last minerals to form and is also associated with the unnamed Zn-Mg carbonate mineral described by Dunn (1986).

Name

Sclarite was named in honor of Dr. Charles B. Sclar of Lehigh University, in recognition of much fine research done at Sterling Hill under his supervision.

Copyright © 1995 by Pete J. Dunn			Website by Herb Yeates
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This page created: January 11, 2001