Hedyphane

Habit
Hedyphane is found as small brilliant crystals in open veins with willemite and calcite, as rough crystals embedded in calcite, and as coarse granular masses. It is white to light buff, has a rough conchoidal fracture and a decidedly greasy luster, is brittle, and has a hardness of about 3. It is optically uniaxial and negative; w = 2.026, e = 2.010, both ±0.01. Under the iron-arc spark it gives a rather indistinct bluish gray fluorescence.

Composition
Hedyphane is a chloroarsenate of lead and calcium-in other words, a calcium-rich mimetite.

**Analysis of hedyphane**
(W. F. Foshag (238), analyst)
PbO	52.77
CaO	14.98
MnO, FeO	0.28
MgO	0.10
ZnO	0.23
As₂O₅	29.94
Cl	2.98
H₂O	0.08
Insoluble	0.17
	101.53
O = Cl₂	0.67
	100.86

The molecular ratio shows a slight excess of calcium over lead, with approximately the general composition of mimetite, hence Foshag defines hedyphane chemically as that member of the chloroarsenates of the apatite group in which calcium is molecularly the dominant metal.

Occurrence
Hedyphane was first described from the Franklin district by Foshag and Gage (238) in 1925. It was found at a depth between 500 and 600 feet on the east side of the ore body in the mine at Franklin, near the point where the two newly described arsenic minerals schallerite and chlorophoenicite were found. It is associated with willemite, rhodonite, native copper, and calcite, in veins an inch or more thick. As the rhodonite and willemite are vividly colored some of the specimens are very showy. In some places hedyphane is the most abundant mineral, enclosing the rest; in other places calcite is the gangue, and there the hedyphane is not uncommonly in rough crystals against the calcite.

The first measurable crystals were described by Palache and Berman (251). They were found with willemite of a peculiar flat, tabular habit in thin veins with small vugs. The high luster of the hedyphane crystals is striking. (See figure 190.)

Figure 190
Bipyramidal crystal of hedyphane showing the forms c(0001), m(1010), x(1011), v(1122), and s(1121). Franklin.

A special interest attaches to the finding of hedyphane at Franklin because it is one of the most abundant of the arsenic-bearing minerals at Langban, Sweden, and had not previously been found elsewhere, except in the similar nearby Swedish deposits.


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