Spinel

This specimen features a distorted octahedral spinel crystal cluster with stepped growth and skeletal-like development, attached to a bit of remaining calcite matrix. The spinel, displays composite growth with multiple malformed octahedra exhibiting interrupted, stacked, and negative growth faces. Notably, spinels from this locality, Dewitts Corners, Ontario, are known to alter partially to corundum, which is evident in this piece as a couple spots on the surface appear to have been altered to white, granular corundum.

This classic and now rarely seen specimen boasts a well-formed, 5 mm black spinel crystal on a calcite matrix, making it an unusual and highly desirable piece for collectors. Dewitts Corners has produced only a limited number of such specimens, making them exceptionally rare on the market today. For further information, refer to George Robinson's analysis published in The Mineralogical Record (Vol. 13, No. 2, March–April 1982, p. 79), where microprobe analyses confirmed these crystals as iron-magnesium spinel (pleonaste).