Loseyite

Habit
Loseyite is found as small, lath-shaped, bluish-white crystals, elongated in the direction of the orthoaxis, more or less loosely grouped in radiate bundles in the cavities of a thin vein composed chiefly of altered pyrochroite and sussexite.

Crystallography
No crystals of loseyite were found that would yield really satisfactory angle measurements, but some very minute lath-shaped crystals were used for approximate data. Several of them, ranging in length from 0.008 to 0.02 inch, were measured, and the angles finally used were those of the best two of these crystals.

Figure 70 illustrates the habit of loseyite.

Figure 70
Crystal of loseyite prismatic parallel to the orthoaxis, showing the c(001), e(011), d(101), s(130), p(136), and r(7.14.2). A, Projection on the vertical plane through the orthoaxis, the crystal being rotated forward to show the base; B, projection on the clinopinacoid.

The orthodome zone is striated parallel to the direction of elongation. The form p(136) is the largest terminal form, but poor images were reflected by its faces because they are etched. The prism s(130) is small but gives brilliant reflections.

Physical properties
The optical properties are biaxial and positive; 2V is 64°; Y = b; a = 1.637, b = 1.648, g = 1.676; r > v (weak). The specific gravity as determined is 3.27 and as computed according to the rule of Gladstone and Dale is 3.25, an indication that the chemical formula adopted is probably correct.

Composition
Loseyite is a hydrous carbonate of manganese and zinc in about equal molecular proportions, with a slight amount of magnesium. The formula adopted was deduced from the following analysis, with a molecular ratio of MnO : ZnO : MgO of 5 : 4 : 1.

**Analysis of loseyite**
	1	2		3
MnO	34.94	0.493*	0.990 = 7 x 0.141	36.40
FeO	0.64	0.009*
ZnO	32.77	0.403*		33.38
MgO	3.42	0.085*		4.14
CO₂	12.59	0.286	= 2 x 0.143	12.90
H₂O	13.83	0.768	= 5 x 0.154	13.18
SiO₂ (insoluble)	0.16	0.003
Mn₂O₃	1.03	0.007
	99.38			100.00

[* Figures reflected in the 0.990 value shown]

1. Loseyite, Franklin. L. H. Bauer (266), analyst.

2. Molecular ratio of 1, omitting silica and manganic oxide.

3. Composition computed from the formula adopted.

Occurrence
Loseyite is found in cavities in a thin vein composed chiefly of altered pyrochroite and sussexite and associated with a few crystals of calcite and a coating of minute hairlike needles that were identified as chlorophoenicite by optical tests. The mineral was discovered in the examination of the material in the Stanton collection. Mr. Stanton, who had collected the specimen in some now inaccessible part of the old mine workings, had made no record of the find, so the exact location is unknown. The mineral is named for S. R. Losey, who had for many years been an ardent collector of the local minerals. It is fully described in the paper by Bauer and Berman (266), who studied and named it in 1929.


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