Spinel is MgAl2O4, isometric, hardness 8. Red spinel was often mistaken for ruby. It also occurs blue, pink, and lavender. It has no cleavage, which makes it durable in jewelry.
This page is only for Spinel. Comments below are for this material.
Robert M. Lavinsky, via Wikimedia Commons
Spinel
Specimen Details
- Hardness (Mohs): 8
- Chemical Formula: MgAl2O4
- Crystal System: Isometric
- Size: Specimen size varies; record the piece, not the species