Svabite

Habit
Svabite has the same crystal habit as apatite, with rough hexagonal prisms, some of which show a rounded pyramidal termination. The color is gray to grayish green, and in its general appearance there is nothing to differentiate it from apatite.

Refractive index
The following table, taken from Bauer and Berman (273), shows the variation of refractive indices and specific gravity with the ratio of phosphate and arsenate in apatite and svabite. The optical data therefore suffice to indicate whether a given specimen is rich or poor in arsenic. There is no other way, except by chemical analysis, to distinguish the two species as they are found at Franklin.

Variation in index of refraction and specific gravity
with composition in the apatite-svabite series
	Phosphate Percent	Arsenate Percent	Index of refraction (w)	Specific gravity
Apatite	42.3	0	1.634	3.20 -
Apatite	28.4	16.2	1.664	3.446
Svabite	12.5	35.2	1.684	3.542
Svabite	0	54.4	1.707	3.54 -

Composition
The following analysis was made on a crystal that proved to be composed of the arsenate and the phosphate in the molecular ratio of about 2 to 1:

**Analysis of svabite**
(L. H. Bauer (273), analyst)
As₂O₅	35.24
P₂O₅	12.54
CaO	45.89
ZnO	1.54
MnO	1.23
MgO	0.84
PbO	0.51
F	1.41
H₂O	1.32
CO₂	Trace
Insoluble	0.29
	100.81
O = F₂	0.59
	100.22

The analysis yields a rather poor molecular ratio for an apatite but is unmistakably that of a member of the apatite group, as confirmed by the crystallographic character.

Occurrence
As far as they have been tested optically or chemically all the apatite-like crystals associated with the Franklin ores have been found to contain arsenic. Those in which As₂O₅ is molecularly in excess of P₂O₅, which include about two-fifths of the crystals examined, have been classed as svabite. As they carne, from all parts of the deposit the mineral is not uncommon in the district, although not in large amount in any one place, Hitherto svabite has been reported only from Harstigen and Jakobsberg, Sweden.


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	This page created: August 12, 2006 6:57 PM