Phosphosiderite is a rare phosphate that is dimorphous (same chemical formula, different crystal system) with the more common phosphate, strengite. It is quite rare in nature as anything other than micros, but this famous old quarry has probably produced the best large crystals, sporadically, over the years. This is surely an older piece, and it hosts an important, lustrous, large crystal to just over 1 cm in length! On a richly colorful matrix of mostly massive phosphate material, this crystal leaps out.