Sigogglinite

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Formula: [Pb₆Zn(OH)₈](SO₄)₃.3H₂O
Valence: [Pb²⁺₆Zn²⁺(OH)₈](S⁶⁺O₄)₃.3H₂O
Hydrated sulphate of lead and zinc
Crystal system: Monoclinic
Specific gravity: 5.107 calculated for the P2/n and 5.085 calculated for the P21/c polytypoid
Hardness: 3
Streak: White
Colour: Colourless
Luminescence: Not fluorescent under UV
Magnetism: Non-magnetic
Solubility: Sigogglinite rapidly turns opaque white (from the formation of PbCl₂) and then slowly dissolves in dilute room temperature hydrochloric acid
Environments

Hydrothermal environments

Sigogglinite is a new mineral, approved in 2024 and to date (June 2026) reported only from the type locality.

Localities

At the type locality, the Redmond Mine, Waterville Lake, Haywood County, North Carolina, USA, sigogglinite was found on material collected underground. The workings were operated sporadically on a small scale until the mid 1940s, when the prospect was abandoned. The vein material is largely composed of massive galena, sphalerite, quartz and muscovite, with lesser chalcopyrite. The mineralisation comprises an epithermal vein system of discontinuous sulphide-bearing quartz lenses located near the contact between a mica schist and a granite gneiss.
New minerals occur in small dissolution cavities as part of a highly localised secondary mineral assemblage. Sigogglinite occurs in association with steverustite, cherokeeite, redmondite, lanarkite and sulfatoredmondite. Sigogglinite is extremely rare and fewer than ten specimens have been found to date (2026).
Two polytypoids are known, sigogglinite-P2/n (7 H₂O per formula unit) and sigogglinite-P21/c (8 H₂O per formula unit). Sigogglinite most commonly forms thick tabular pseudohexagonal crystals, to about 400 microns across, with striated faces (CJMP 64.261-274).
Sigogglinite from the Redmond Mine - Image

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