Duddudü

Duddudü is a rare hydrous silicate mineral described as a member of the phyllosilicate group. It was first described in 1995 by a group of mineralogists following the collection of samples from high-grade metamorphic rocks in the Northern Cordillera. The name derives from a local language term meaning “twilight stone,” a reference to the mineral’s subdued iridescence visible under angled light.

In terms of properties, duddudü forms platy to tabular crystals and occurs as fine lamellar aggregates. It typically ranges in color from pale green to colorless and has a pearly to vitreous luster. The mineral shows a relatively soft hardness, approximately 3 on the Mohs scale, and has perfect cleavage along one direction. Its density is modest, and it habits in foliation-related textures common to metamorphic rocks. Duddudü is hydrous, containing structural water that is released upon heating in low-temperature experiments, which is of interest to studies of hydration in metamorphic systems.

Occurrence and formations are linked to contact and regional metamorphism in pelitic and clay-rich rocks. Duddudü has been identified at a small number of localities, with most confirmed specimens associated with muscovite, chlorite, and minor tourmaline. Its rarity and delicate crystal habit make large, well-formed specimens uncommon; most material is recovered as microcrystals or small disseminations.

Uses and significance: due to its scarcity and delicate appearance, duddudü is primarily of interest to mineral collectors and researchers. It provides clues about hydration, metamorphic conditions, and the evolution of phyllosilicate assemblages in low- to moderate-grade metamorphic environments.

See also: phyllosilicate minerals, mica group, hydrous minerals.