Spinel

This specimen features a 26 mm distorted octahedral spinel crystal with pronounced stepped growth and skeletal-like development, perched on a bit of remaining calcite matrix. The spinel displays composite growth, with a multitude of malformed octahedra showing interrupted, stacked, and negative growth faces. Notably, spinels from the Dewitts Corners locality in Ontario are known to partially alter to corundum, although it's unclear whether that is the case here and may warrant further investigation.

This is a classic and now rarely seen specimen from a locality that produced only a limited number of such pieces. Its size, crystal form, and matrix association make it an especially desirable example for collectors. For more detail on the mineralogy of Dewitts Corners spinel, refer to George W. Robinson’s analysis published in The Mineralogical Record (Vol. 13, No. 2, March–April 1982, p. 79), where microprobe data confirmed the material as iron-magnesium spinel (pleonaste).