Agravaras

Agravaras are a class of rare hydrothermal mineral aggregates found in volcanic regions. The term refers to specimens that form layered, botryoidal to fibrous aggregates composed of hydrated sulfates and silicates. They are typically distinguished by iridescent surface coatings and a pale blue-green to white coloration.

Etymology and naming in the in‑world literature trace the term to the field geologist Dr. Leora Agrava, who first described the assemblages in 1987 in the Solarian Basin. The plural agravaras denotes multiple specimens or localities sharing the characteristic mineralogy and morphology, while a singular form, agravar, is used for an individual specimen.

Occurrence and formation occur in hydrothermal veins within andesitic to rhyolitic host rocks, often near fumarolic or vent-related zones. Agravars precipitate from sulfur-rich fluids as they cool and interact with wall rocks, producing a mixed assemblage of sulfates and silicates. They are commonly associated with gypsum, melanterite, and related alteration minerals.

Physical and chemical properties: agravaras have a hardness around 3 to 4 on the Mohs scale and a density near 2.8 to 3.2 g/cm3. Colors range from pale blue-green to white, with a vitreous to pearly luster. Many specimens display an iridescent patina due to thin oxide coatings. X-ray diffraction patterns often show broad, poorly crystalline peaks, reflecting microcrystalline to fine-grained textures. The chemical composition is dominated by hydrated sulfates with silicate inclusions and trace metals.

Classification and varieties: there is no universally formal mineral species under the name agravara; in field guides two described varieties are agravar alba (white) and agravar viridis (green), distinguished primarily by color and trace impurities.

Uses and significance: agravaras are of interest to mineral collectors and researchers studying hydrothermal systems, fluid pathways, and ore-forming processes. They are occasionally cut for display or jewelry in highly limited markets.