Home > American Minerals II – April 7 > MS1555 Spinel
Spinel - Sold
- Crazy Sphinx claim
- Helena
- Lewis & Clark County
- Montana
- U.S.A.
- 2.5 by 2.1 by 1.7 cm – Thumbnail specimen (fits into a 2.5 cm cube)
Spinel is a magnesium aluminum oxide, typically in octahedral crystals. The name spinel comes from the French spinelle for thorn (or point) alluding to the six points of an octahedron. While pure synthetic spinel is colorless, natural samples incorporate various metal impurities which led to a wide range of colors, including red coloration reminiscent of fine ruby (Hughes, 2010). Blue coloration in natural spinel is rather unusual; causes involve cobalt ions (Co2+) and iron ions (either Fe2+ or Fe3+) and various combinations thereof (D'Ippolito et al., 2015).
This specimen consists of a blue pinel octahedron 1.7 by 1.1 by 2.0 cm, protruding out of feldspar matrix. The spinel crystal is complete, but shows contacting on one edge. This specimen collected by Bart Cannon (1950-2019), a mineralogist specializing in minerals of Washington state, and author of the 1976 Minerals of Washington.
