Diagnostic Features
1. Hardness: 5,5
2. Streak: Greenish white to none
3. Luster: Nonmetallic
4. Specific Gravity: 3.1
5. Cleavage: 2 lengthwise directions at 56 and 124 degrees
6. Fracture: None
7. Other: Commonly dark green to brownish green. Cleaves into lengthwise, prismatic crystals.
Identification Tips
Amphiboles and pyroxenes are often mistaken for one another due to their generally similar appearance ad color. However, there are important distinguishing characteristics by which the two may be distinguished.
1. Amphibole has strongly oblique cleavage whereas pyroxene possesses orthogonal cleavage.
2. Amphiboles are more common in felsic igneous rocks whereas pyroxenes are ubiquitous to mafic and ultramafic igneous rocks.
3. Amphiboles are common in metamorphic rocks whereas pyroxenes are rare in such rocks.
4. Amphiboles tend to cleave into splintery fragments when struck, whereas pyroxenes do not.
