Oligoclase
Series / solid solution
Oligoclase is a sodium-rich plagioclase feldspar. Compositions vary between the end-member species Albite and Anorthite.
Photos
About Albite (major)
Full reference data — crystallography, X-ray diffraction, and cited physical properties — is on the Albite species page.
| Formula | Na(AlSi3O8) |
|---|---|
| Hardness (Mohs) | 5.5 |
| Specific gravity | 2.63-2.66 |
| Density (calculated) | 2.621 |
| Crystal system | triclinic |
| Color range | red, white, yellow |
| Streak | white |
About Anorthite (minor)
Full reference data — crystallography, X-ray diffraction, and cited physical properties — is on the Anorthite species page.
| Formula | Ca(Al2Si2O8) |
|---|---|
| Hardness (Mohs) | 6-6.5 |
| Specific gravity | 17 |
| Density (calculated) | 2.797 |
| Crystal system | triclinic |
| Color range | gray, red, white |
| Streak | red |