BARITE

BaSO₄ 
Orthorhombic

	Figure 24-2. Crystal drawing of barite from the Trotter Mine in Franklin. Drawing is from Palache (1935) who provided crystallographic data.

Barite, a barium sulfate mineral of the barite group, was noted by Genth (1891) and Penfield (1897) from Franklin, but was surely known earlier. Palache (1935) summarized the extant data on barite, and little additional work has been done. Isotopic data for Sterling Hill barite were given by Davis (1993).

Description

Barite from Franklin and Sterling Hill occurs as both fine crystals in vugs and veins and as massive material. Crystals are commonly small, < 5 mm, but some are larger. There is much variation in the crystal habit, varying from equant to platy to bladed to prismatic (Figures 24-2, 24-3, and 24-4). Barite crystals from high-temperature parageneses tend to be tabular, and those from later secondary veinlets are commonly prismatic, but exceptions to both observations are known. Prismatic crystals commonly have slightly curved faces.

The color of barite varies considerably; blue, blue-white, white, yellow, and brown specimens are known. The luster is vitreous to satiny to dull, and there are three directions of cleavage at right angles. No physical, optical, or chemical data have been published. Barite fluorescence in shortwave ultraviolet varies (white, blue-white, and light brownish-yellow colors are known); the fluorescence in longwave is weaker.

Occurrence and paragenesis

Barite is common at Franklin and is apparently more restricted in occurrence at Sterling Hill. Although occurring in small quantities, it is so pervasive as to be the principal sulfate mineral at these deposits. Among the various occurrences, it is most abundant where associated with calcite in large masses.

	Figure 24-3. Superb barite crystals from Franklin; crystal at right appears to have willemite crystal “piercing” it. Each crystal is 0.3 mm in maximum dimension.

At Franklin, barite occurs as visible crystals in vein assemblages. Calcite is the most commonly associated mineral but, due to the near-ubiquitousness of barite, numerous minerals are associated with it, and only a few are noted here. The most attractive occurrence of Franklin barite is a vein assemblage with bright pink hodgkinsonite contrasting sharply with bright white platy barite crystals and forming one of Franklin’s mineral treasures (Figure 15-48). Superb stout white crystals, similar to those illustrated by Palache, were found in a rare assemblage (Figure 12-43) of superbly crystallized willemite, tephroite (Figure 15-3), hodgkinsonite (Figure 15-52), and pyrobelonite (Figures 25-33 and 25-34).

	Figure 24-4. Cluster of subparallel, slightly-offset barite crystals from Sterling Hill. Field of view is 0.8 mm in maximum dimension.

Barite is also found with hancockite, clinohedrite, prehnite, and manganaxinite in highly recrystallized material; with calcite as 3-4 cm rock-locked crystals with rhodonite in primary assemblages; and in many other associations. Palache (1935) mentioned barite from the Trotter and Parker Mines.

At Sterling Hill, barite is found in smaller amounts in general, and much may be unrecognized. It most commonly occurs in veins, as microcrystals associated with carbonates, arsenates, and numerous other minerals. It also occurs as localized large masses with calcite; both are fluorescent. An occurrence in a veinlet assemblage in wollastonite-bearing rocks was described by Jenkins (1994).

 

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