KOLICITE Chapter15. Nesosilicates

KOLICITE

Mn₇(OH)₄[As₂Zn₄Si₂O₁₆(OH)₄]
Orthorhombic, Cmca, a = 18.59, b = 8.789, c = 12.04 Å, Z = 4.




	Figure 15-56. Tabular, textured kolicite crystal from Sterling Hill. Field of view is 0.1 mm in maximum dimension.

Kolicite was initially described by Dunn et al. (1979b) using material from Sterling Hill and noting the occurrence at Franklin, which was intimately associated with holdenite.

Crystal structure

The crystal structure was described by Peacor (1980), who confirmed the cubic closest packing of anions in the structure and found As, Zn, and Si to be tetrahedrally coordinated, forming continuous vertex-sharing slabs oriented normal to c. These are linked with units of seven edge-sharing Mn octahedra to form a three-dimensional structure. Peacor also described a basic unit of structure common to both kolicite and holdenite.

Description

Kolicite occurs as euhedral crystals with varied form development. Crystals from the first occurrence are markedly tabular and have, for the most part, extensively textured faces.




	Figure 15-57. Tabular, textured kolicite crystal from Sterling Hill. Field of view is 0.1 mm in maximum dimension.		Figure 15-58. Equant, highly-modified kolicite crystals from the 1982 find at Sterling Hill. Field of view is 0.8 mm in maximum dimension.

Kolicite is orange and has a vitreous luster and no cleavage. The density is 4.17 g/cm³ (meas.), 4.20 g/cm³ (calc.). The hardness is 4½; the mineral is brittle and has an even fracture. Optically, kolicite is biaxial, negative, 2V_x = 78^o (meas.), 74^o (calc.), with a = 1.779, b = 1.786, and g = 1.790. Pleochroism is strong with Z = light yellow, Y = yellowish orange, and X = colorless to pale yellow; dispersion is strong, r < v; absorption is Z = Y > X. There is no discernible fluorescence in ultraviolet. Broken crystals resemble garnet, but the anisotropism and pleochroism are diagnostic.




	Figure 15-59. Superb euhedral crystal of kolicite from Sterling Hill. Field of view is 0.3 mm in maximum dimension.		Figure 15-60. Pseudocubic crystals of kolicite in a nested cluster on a larger kolicite crystal, from the 1982 find at Sterling Hill. Field of view is 0.4 mm in maximum dimension.

Composition

Kolicite is a manganese zinc arsenate silicate hydroxide mineral. Minor Fe and Mg proxies for Mn and Zn. Analyses of the type material (#143785) and the slightly magnesian material of the subsequent 1982 find (#149556) are given in Table 4 and are in good agreement with the idealized composition.

Occurrence and paragenesis




	Figure 15-61. Tabular, textured kolicite crystal from Sterling Hill. The field of view is 0.1 mm in maximum dimension.

Kolicite is a mineral of the secondary veins. It was first found in the 1020 longitudinal stope, about 30 feet above the 1400 level, within the central zincite zone, in the east branch of the west limb of the Sterling Hill orebody. It was found in a shear zone, as evidenced by slickensides. It occurs as euhedral crystals (Figures 15-56, 15-57, 15-59, and 15-61) on fracture surfaces in calcite-poor red-willemite/franklinite ore. Kolicite is associated with secondary sonolite and friedelite and is younger than these minerals; it formed contemporaneously with secondary willemite. Kolicite was later found on the 1200 and 1300 levels.

Another occurrence was found by John Kolic in 1982; crystals from this occurrence are predominantly equant in habit (Figures 15-58 and 15-60). Kolicite from this second occurrence was associated with holdenite and mcgovernite. It was found in the 1020 stope, 40 feet below the 1200 level, in the west limb (outer zincite zone) of the Sterling Hill orebody, outside the central zincite zone where the first material was found, at a point where a shear connected this area with the central zincite zone. Here both holdenite and kolicite occurred in euhedral crystals.

Kolicite was also verified by the writer on several holdenite samples from Franklin, and thus was first found, but unrecognized, likely in 1913. Kolicite and holdenite have been found in contact in all three of the known occurrences. In large part due to the paucity of samples, there has been no direct study of the crystallographic relations of kolicite and holdenite in contact.

Name

Kolicite was named in honor of John Kolic, a senior miner at Sterling Hill and a collector and supporter of the science. John Kolic is of keen intellect; he has preserved many uncommon and important parageneses and has found a number of new mineral species.

FOOTER LBI




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

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This page created: January 11, 2001