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| Hornblende
- (Na,K)0-1Ca2(Mg,Fe,Al)5(Si6-7.5Al2-0.5O22)(OH)2 |
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(select an
image, left-mouse click & drag to rotate)
Physical
Properties of Hornblende
Color |
Dark green to
black |
| Luster |
Non-metallic,
vitreous |
| Streak |
Gray to greenish
gray |
| Cleavage |
2 directions,
meet at 60 and 120 degree angles |
| Specific
Gravity |
3.02 - 3.59 |
| Hardness |
5 - 6 |
| Distinguishing
Characteristics |
60 - 120 cleavage,
Dark Color |
Optical
Properties of Hornblende
Color |
Green or Brown
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| Pleochroism |
Strong; Dark green
to light green or dark brown to light brown |
| Relief |
Moderate to high
positve relief (n = 1.6 - 1.73) |
| Interference
Colors |
Low second order
colors (Birefringence = 0.018 - 0.025) |
| Opical
System |
Biaxial positive
or negative |
| 2V Angle
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35 - 130 degrees
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| Distinguishing
Characteristics |
60 - 120 cleavage;
Strong Pleochroism; Extinction at 30 degrees to upper polarizer |
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