Spray of Columbite Crystals in Topaz
A probable columbite inclusion in beryl was featured in a recent Quarterly Crystal, demonstrating the striking form these minerals can display (Spring 2023 G&G Micro-World, pp. 90–91). It was only fitting to follow up with a look at the same inclusion hosted by a different mineral.
The cluster of bladed columbite crystals in the figure above, identified via Raman spectroscopy, was found in an 8.91 ct colorless topaz. The thinner crystals allowed the brown bodycolor to show through, while the thicker, sword-like center crystal appeared black and opaque. Thin-film interference was observed between the host and inclusion when illuminated with oblique lighting, adding some welcome color to an otherwise featureless crystal face. While columbite has been previously described in topaz (Fall 2009 G&G Lab Notes, pp. 212–213; E.J. Gübelin and J.I. Koivula, Photoatlas of Inclusions in Gemstones, Volume 2, Opinio Publishers, Basel, Switzerland, 2005, pp. 263, 738), this is the most dramatic example observed by the author.