Derbylite

Lamellar to prismatic crystals of derbylite displaying striking metallic iridescence in blue-violet, bronze and golden tones, embedded in a white saccharoidal quartz matrix with iron oxides. The crystals show well-developed longitudinal striations and partially coated terminations by microcrystalline hematite and goethite, typical of the oxidizing hydrothermal environment of the classic Buca della Vena deposit.

Derbylite, a rare iron-titanium antimonate oxyhydroxide (Fe²⁺Fe³⁺₂TiSbO₇(OH)), is a characteristic species of high-oxidation supergene zones in complex polymetallic vein systems. At Buca della Vena it occurs in association with stibiconite, valentinite, rutile, hematite and various Ti- and Sb-bearing secondary phases.

Italian specimens are particularly prized for their well-formed crystals and their vivid surface iridescence, produced by thin oxidation layers and optical interference effects. This example is a textbook illustration of the tabular-prismatic habit and internal lamellar structure of derbylite, making it highly desirable for advanced collectors of antimony minerals and for studies of Alpine supergene parageneses.

In a box 2.8x2.8cm, labelled

FoV : 2.8mm

Ex Cauzzi 1987