page_title: Hilgardite
hierarchical_section_title: Hilgardite
caption_attribution_description: English: Hilgardite, Boracite Locality: Boulby Mine, Loftus, North Yorkshire, England, UK (Locality at mindat.org) Size: 5.5 x 4.5 x 3.4 cm. Microcrystalline red-orange hilgardite encasing boracite, from this classic locale that was revisited by mineral collectors in the late 90s. Ex. Martin Zinn Collection. Deutsch: Hilgardit, Boracit Fundort: Cleveland Potash Mine, Loftus, North Yorkshire, England, Vereinigtes Königreich (Fundort bei mindat.org) Größe: 5.5 x 4.5 x 3.4 cm.
context_page_description: Hilgardite is a borate mineral with the chemical formula Ca₂B₅O₉Cl·H₂O. It is transparent and has vitreous luster. It is colorless to light pink with a white streak. It is rated 5 on the Mohs Scale. It crystallizes in the triclinic crystal system. Crystals occur as distorted tabular triangles and are hemimorphic, polytypes exist.
  It was named for geologist Eugene W. Hilgard. It was first described in 1937 for an occurrence in the Choctaw Salt Dome of Iberville Parish, Louisiana, US. It occurs as an uncommon accessory mineral in evaporite deposits and salt domes worldwide. In addition to the type locality it has been reported in Wayne County, Mississippi and in the Louann Salt Formation, Clarke County, Alabama in the United States and at the Penobsquis and Salt Springs evaporites, near Sussex, New Brunswick, Canada. In Europe it is reported from the Konigshall-Hindenburg potash mine near Göttingen, Lower Saxony, Germany and in the Boulby potash mine, Whitby, Yorkshire, England. In Asia it is reported from the Chelkar salt dome, Uralsk district, Kazakhstan; the Ilga Basin, eastern Siberia, Russia and the Sedom Formation, Mount Sedom, Dead Sea, Israel.
context_section_description: Hilgardite is a borate mineral with the chemical formula Ca₂B₅O₉Cl·H₂O. It is transparent and has vitreous luster. It is colorless to light pink with a white streak. It is rated 5 on the Mohs Scale. It crystallizes in the triclinic crystal system. Crystals occur as distorted tabular triangles and are hemimorphic, polytypes exist.
  It was named for geologist Eugene W. Hilgard (1833–1916). It was first described in 1937 for an occurrence in the Choctaw Salt Dome of Iberville Parish, Louisiana, US. It occurs as an uncommon accessory mineral in evaporite deposits and salt domes worldwide. In addition to the type locality it has been reported in Wayne County, Mississippi and in the Louann Salt Formation, Clarke County, Alabama in the United States and at the Penobsquis and Salt Springs evaporites, near Sussex, New Brunswick, Canada. In Europe it is reported from the Konigshall-Hindenburg potash mine near Göttingen, Lower Saxony, Germany and in the Boulby potash mine, Whitby, Yorkshire, England. In Asia it is reported from the Chelkar salt dome, Uralsk district, Kazakhstan; the Ilga Basin, eastern Siberia, Russia and the Sedom Formation, Mount Sedom, Dead Sea, Israel.
caption: Microcrystalline red-orange hilgardite encasing white boracite, from Boulby Mine, Loftus, North Yorkshire, England. Size: 5.5 × 4.5 × 3.4 cm.
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