Augite is a clinopyroxene. Clinopyroxenes and orthopyroxenes are easily distinguished in thin section by their extinction angles: clinopyroxenes have inclined extinction, and orthopyroxenes have parallel extinction.
Physical Properties |
|
| Chemical formula | (Ca,Mg,Fe,Na)(Mg,Fe,Al)(Si,Al)2O6 |
| Class | Inosilicate Single chains of linked tetrahedra |
| Crystal system | Monoclinic |
| Habit | Stubby prisms with octagonal or square cross sections |
| Color | Black, dark green |
| Hardness | 5 to 6 |
| Specific gravity | 3.2 to 3.4 |
| Cleavage | Two perfect {110} |
| Fracture | Uneven |
| Luster | Vitreous |
| Transparency | Transparent to translucent |
| Streak | White |
Optical Properties |
|
| PPL | Shades of light brown, yellow-brown, or green May be weakly pleochroic |
| XPL | 3rd order interference colors Inclined extinction |
| δ | 0.030 |
| Twinning | May show simple or polysynthetic twins |
| Extinction | Inclined |
| after Perkins, 328 |
Augite in Hand Sample
Augite
Augite phenocrysts from Mt. Vesuvius
Scanning electron micrograph of augite
Another scanning electron micrograph of augite
Augite in Thin Section
Thin Section GigaPans
Augite, plane polars
Augite, crossed polars
