Lollingite

Figure 16
Crystal of lollingite showing the forms c(001), b(010), m(110), c(101), l(011), z(012), and s(111). Trotter shaft. A, Plan; B, clinographic projection.

The crystals were of unusually fine quality for this mineral, and the axial ratio–a : b : c = 0.5438 : 1 : 1.130–derived from their measurement, is thought to be better than any previously computed.

Composition
A chemical analysis of the Franklin lollingite was made by Bauer, using 0.4 g of carefully selected crystals, with the following result:

**Analysis of lollingite**
(L. H. Bauer (247), analyst)
	Percent	Molecular ratio
As	69.80	0.933*	1.78
S	0.21	0.007*
Fe	29.40	0.530	1
	99.41

[*Figures reflected in the value 1.78 shown at right]

The slight deficiency of the analysis is due to the presence of a small and undetermined amount of calcite. Sulphur is practically negligible. There is insufficient arsenic, as shown by the molecular ratio, to give quite the 2 to 1 ratio of lollingite. Such a deficiency is common in analyses of this mineral and has usually been accounted for by assuming the presence of more or less of the leucopyrite molecule, Fe₃As₄. In this analysis computation indicates the assumed presence of 14 percent of leucopyrite. The specific gravity is 7.505 (Buerger).

Occurrence
Lollingite was found at Franklin in the Buckwheat mine, where granular masses intermingled with franklinite were somewhat rare. It was also recorded, in brilliant tin-white crystals (see Figure 14), by Brush (100), accompanying the unique cubical gahnite that he described.

Figure 14
Pseudo-dodecahedral crystal of lollingite showing the prism m(100), the macrodome e(101), and the brachydome z(012). Buckwheat mine.

At the Trotter shaft tin-white crystals, too rough for measurement, were found sparsely with gahnite in the limestone wall rock. The specimens described by Bauer and Berman (247) were found in 1926 in a drift on the 750-foot level, north. The crystals are sparsely embedded in white limestone of medium grain, together with crystals of gray pyroxene and scattered dots of franklinite. The lollingite crystals are complete individuals, of a brilliant tin-white color, and range in size from tiny specks to crystals with a diameter of an eighth of an inch. They break freely and cleanly from the matrix, and the brilliance of their luster marked them at once as suitable for crystallographic study. They are shown in Figures 15 and 16.

Figure 15
Crystal of lollingite of dodecahedral habit, showing the forms m(110), e(101), and l(011). Trotter shaft.


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