Barysilite

Physical properties
Barysilite is found in massive granular form, intimately mixed with garnet and willemite and associated with axinite and hardystonite. Its color is faintly pinkish white. The perfect cleavage is basal. It is uniaxial and optically negative, and, for sodium light, w = 2.033 and e = 2.015, both ±0.004.

Composition
The original barysilite from Franklin (244) was so scarce that difficulty was encountered in getting enough for analysis, and the sample analyzed contained garnet and willemite. Later an adequate sample was obtained and was analyzed by Mr. Bauer. Both analyses are given below.

**Analyses of barysilite**
	1	2	3
SiO₂	18.73	16.84	0.280	= 2 x 0.140
Al₂O₃	1.76	0.59	0.006
PbO	71.14	77.35	0.347*
MnO	3.97	3.33	0.047*
FeO	0.24	0.23	0.003*
CaO	0.10	0.21	0.004*	0.424 = 3 x 0.141
MgO	1.02	0.78	0.019*
ZnO	1.69	0.30	0.004*
H₂O	0.73	0.07	0.004
	99.38	99.70

[* Figures reflected in the value 0.424 shown.]

1. Barysilite, Franklin. E. V. Shannon (244), analyst.

2. Barysilite, Franklin. L. H. Bauer (273), analyst.

3. Molecular ratio of no. 2.

The molecular ratio shows the mineral to be a sub-silicate of lead, containing some manganese and small amounts of magnesium, zinc, calcium, and iron.

Barysilite is easily fusible to a blackish-purple glass. It is slowly decomposed by hot concentrated hydrochloric, acid with the separation of silica.

Occurrence
Barysilite was found in a few small masses on the picking table at Franklin, and its lead-bearing nature was first recognized by the chemists of the New Jersey Zinc Company. It occurs as thin films or veinlets in the ore, associated with garnet, willemite, axinite, and hardystonite.

Barysilite is one of the typical lead silicates of the Langban and Pajsberg mineral associations, and its discovery at Franklin marked the first time that it has been found at any other locality.


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