This specimen has unusually large, well-formed, sharp crystals to over 1 cm, and is part of the piece illustrated in Barlow's book on page 349 (I trimmed that specimen when I bought it in 1998 and just got this half back in a collection purchase, funny enough). It has a long history dating to a one-time find on the mine dumps in the 1980s. These are regarded as among the best of species. Illustrated in The John Barlow Mineral Collection, page 349.