Mooreite

Habit
Mooreite forms glassy white tabular crystals in cavities and crevices in pyrochroite, partly intergrown with fluoborite. The crystals are tabular parallel to the clinopinacoid (see figure 199) and are generally grouped in subparallel aggregates.

Figure 199
Crystal of mooreite tabular parallel to the clinopinacoid, showing the forms c(001), a(100), b(010), d(101), f(102), e(011), and s(111). Sterling Hill.

Some small doubly terminated crystals of almost ideal development were seen. A bluish-white variety of slightly different composition was found in some of the crevices but not in crystals.

Physical properties
Mooreite is clear glassy white and has a perfect clinopinacoidal cleavage. Its specific gravity is 2.470. The variety called d-mooreite is bluish-white and granular and its cleavage is less perfect. Its specific gravity is 2.665. The hardness of both varieties is about 3.

Both varieties are optically biaxial and negative. In mooreite 2V = 50° ±; X = b ; Z /\ c = 44° ; r > v (perceptible); a = 1.533, b = 1.545, g = 1.547. In d-mooreite 2V = 40° ±; a = 1.570, b = 1.584, g = 1.585.

Composition
Mooreite is a basic hydrous sulphate of magnesium, zinc, and manganese. There are no known minerals to which it is closely related. The two varieties differ chiefly in the relative proportion of the three metallic bases. Which of the two is chemically the more typical of the species cannot be decided, and possibly one of them is being developed at the expense of the other.

**Analyses of mooreite**
	1	2		3	4
MgO	25.38	0.629*	1.096 = 8 x 0.137	17.27	0.427†	1.003 = 7 x 0.143
MnO	11.93	0.167*		17.98	0.253†
ZnO	24.58	0.300*		26.30	0.323†
SO₃	10.99		0.136 = 1 x 0.136	11.64		0.145 = 1 x 0.145
H₂O	27.12		1.506 = 11 x 0.137	26.39		1.466 = 10 X 0.146
B₂O₃				Present
SiO₂				0.08
	100.00			99.66

[* Figures reflected in the value 1.096 shown.]

[† Figures reflected in the value 1.003 shown.]

1. Average of two analyses, recomputed to 100 percent after deducting unessential constituents. L. H. Bauer (267), analyst.

2. Molecular ratio of no. 1.

3. d–mooreite. L. H. Bauer (267), analyst.

4. Molecular ratio of no. 3.

From the molecular ratios may be derived the following formulas for the two varieties: Mooreite, 7R(OH)₂.RSO₄.4H₂O, in which R is Mg : Zn : Mn = 4 : 2 : 1 ; d-mooreite, 6R(OH)₂.RSO₄.4H₂O, in which R is Mg : Zn : Mn = 5 : 4 : 3.

Occurrence
Mooreite is found in cavities and crevices in pyrochroite in a vein in normal calcite-franklinite-willemite ore at Sterling Hill. It was described in 1929 by Bauer and Berman (267), who named it for Gideon H. Moore, late chemist of the Passaic Zinc Co., who first described the minerals brushite, chalcophanite, and hetaerolite.


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