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(select an
image, left-mouse click & drag to rotate)
Physical
Properties of Plagioclase
Color |
White to Gray,
Possible blueish in Ca-rich varieties |
| Luster |
Non-Metallic,
Vitreous to pearly |
| Streak |
White |
| Cleavage |
2 directions intesecting
at nearly 90 degrees, 3rd poor cleavage may be visible |
| Specific
Gravity |
2.6 - 2.76 |
| Hardness |
6 - 6.5 |
| Distinguishing
Characteristics |
Parallel striations
on cleavage faces |
Optical
Properties of Plagioclase
Color |
Colorless |
| Pleochroism |
None |
| Relief |
Low positve or
negative relief (n = 1.527 - 1.59) |
| Interference
Colors |
Low first order
gray (Birefringence = 0.007 - 0.013) |
| Opical
System |
Biaxial postive
or negative |
| 2V Angle
|
45 - 102 degrees
|
| Distinguishing
Characteristics |
Low relief; Polysynthetic
twinning |
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