MINERALS INDEX
Barylite |
| Be2BaSi2O7 |
| Orthorhombic |
Character
At Franklin barylite is found in plates embedded in hedyphane with some willemite. The
plates are more or less brecciated and are cemented with thin films of serpentine. The
mineral is white, of hardness 7, and of specific gravity 4.066 ±0.002. It shows two good
cleavages, one basal and the other parallel to the macropinacoid. It has a vivid blue
fluorescence in ultraviolet light. Barylite is optically biaxial and negative; 2V=
70° ±2° (measured on a Fedorof stage); a = 1.695, b
= 1.702, g = 1.708, all
±0.002; the cleavages are normal to g and b
(Berman).
The above data differ somewhat from those given by Aminoff for the Langban mineral, which has somewhat lower refractive indices, a slightly lower specific gravity, and in most specimens is positive. Also Aminoff reports but one cleavage.
Composition
Barylite is a silicate of beryllium and barium of simple composition. The
material analyzed was extremely pure and gave an almost exact molecular ratio
of BeO : BaO : SiO2 = 2 : 1 : 2. It is worthy of note that the
beryllium content of barylite is slightly higher than that of beryl, the commonest
beryllium mineral.
|
1 |
2 |
3 |
|
| SiO2 |
36.42 |
0.606 = 2.00 |
37.14 |
| BeO |
15.77 |
0.630 = 2.08 |
15.47 |
| BaO |
46.49 |
0.303 = 1.00 |
47.39 |
| FeO |
0.19 |
||
| MgO |
0.29 |
||
| ZnO |
(a) |
||
| PbO |
0.11 |
||
| H2O at 110° |
0.40 |
||
|
99. 67 |
100.00 |
| a Present. |
| 1. Barylite, Franklin. L. H. Bauer (272), analyst. |
| 2. Molecular ratio of no. 1. |
| 3. Composition computed from the formula. |
Occurrence
Barylite was first found at Franklin in 1929, on the picking table. Later
it was located in the mine in pillar 960, 20 feet below the hanging wall.
The specimens seen by the author clearly part of a well-layered vein, the
succession of layers from a surface of ore being brown calcite and native
copper; gray calcite; a thin zone of willemite and serpentine; white calcite
in curved rhombohedrons, strongly fluorescent in ultraviolet light; and barylite,
hedyphane, and willemite. Attention was first called to the barylite by its
vivid blue fluorescence.
Barylite was first described in 1880 as an aluminum-barium silicate found at Langban with hedyphane. In 1923 Aminoff discovered that the supposed alumina is really beryllia. The discovery at Franklin, described by Palache and Berman (272), is the second reported occurrence of this mineral.
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Website
© by Herb Yeates 1997-2006.
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This
page created: August 12, 2006 5:45 PM
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