Hiortdahlite

specimen number:
9302274

location:
Langesundsfjorden, Norway

description:
Yellowish prismatic crystalline embedded within matrix. Excellent thumbnail for this rare species. The specimen comes with photocopies of the previous labels from the Naturhistoriska Riksmuseet, ex Flink collection, as seen at the end of the video.

Hiortdahlite is a rare sorosilicate mineral belonging to the woehlerite group, primarily known from alkaline igneous environments such as the nepheline syenite pegmatites of the Langesundsfjord in Norway. Geologically, it forms as a primary crystallization product in these highly evolved, silica-undersaturated rocks, where it is often associated with other rare-earth and zirconium-bearing minerals like zircon, fluorite, and lavenite. The mineral typically occurs as small, brittle, triclinic crystals or grains that exhibit a range of colors from pale yellow to light brown or amber. It is chemically complex, composed of calcium, sodium, zirconium, and fluorine, and is structurally distinguished by its specific arrangement of silicate tetrahedra and octahedral layers. Historically, hiortdahlite was first described in 1889 by the Norwegian mineralogist W.C. Broegger, who named it in honor of Thorstein Hiortdahl, a pioneering chemist and mineralogist.

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