A truly exceptional specimen containing large, coarse, royal blue subhedral crystal clusters of diaboleite, a lead-copper chloride hydroxide, along with several large, sharp, well-formed crystals of leadhillite to 1.4mm! Leadhillite is a rare lead sulfate-carbonate hydroxide and the Mammoth-St. Anthony mine is an important locality for the species! The prominent leadhillite crystals are blocky, pseudo-orthorhombic and exhibit nice adamantine luster. The specimen is accented by several small clusters of blue-green caledonite on the bottom and one large, splendid, lustrous, striated crystal of caledonite to 1 cm on the right side in direct association with diaboleite, leadhillite and malachite. Malachite is present as bright green, dull, velvety patches on the specimen covering leadhillite. A very classic suite of these rare secondary carbonate-sulfate minerals from this famous locality undoubtedly originating from the Collins Vein on the 400 level. Ex. William Pinch collection with label. A significant rarity and ALSO a display-quality specimen for any collection, this is a major historic piece.