Natron - Geological Occurrence

Geological Occurrence

Geologically, the mineral natron as well as the historical natron are formed as transpiro-evaporite minerals, i.e. crystallizing during the drying up of salt lakes rich in sodium carbonate. The sodium carbonate is usually formed by absorption of carbon dioxide from the atmosphere by a highly alkaline, sodium-rich lake brine, according to the following reaction scheme:

NaOH_(aq) + CO₂ → NaHCO_3(aq)

NaHCO_3(aq) + NaOH_(aq) → Na₂CO_3(aq) + H₂O

Pure deposits of sodium carbonate decahydrate are rare, due to the limited temperature stability of this compound and due to the fact that the absorption of carbon dioxide usually produces mixtures of bicarbonate and carbonate in solution. From such mixtures, the mineral natron (and also the historical one) will be formed only if the brine temperature during evaporation is maximally about 20 °C (68 °F) – or the alkalinity of the lake is so high, that little bicarbonate is present in solution (see reaction scheme above) – in which case the maximum temperature is increased to about 30 °C (86 °F). In most cases the mineral natron will form together with some amount of nahcolite (sodium bicarbonate), resulting in salt mixtures like the historical natron. Otherwise, the minerals trona or thermonatrite and nahcolite are commonly formed. As the evaporation of a salt lake will occur over geological time spans, during which also part or all of the salt beds might redissolve and recrystallize, deposits of sodium carbonate can be composed of layers of all these minerals.

The following list may include geographical sources of either natron or other hydrated sodium carbonate minerals:

• Africa
  • Chad
    • shores of Lake Chad
  • Egypt
    • Wadi El Natrun
  • Ethiopia
    • Showa Province
  • Niger
    • Bilma
• Europe
  • Hungary
    • Bács-Kiskun County, (Great Hungarian Plain)
    • Szabolcs-Szatmár-Bereg County (Great Hungarian Plain)
  • Italy
    • Campania,
    • Province of Naples
    • Somma-Vesuvius Complex
  • Kola Peninsula, northern Russia
    • Khibiny Massif
    • Lovozero Massif
      • Alluaiv Mountain
      • Kedykverpakhk Mountain
    • Umbozero Mine
  • England, UK
    • Cornwall
    • St Just District
    • Botallack – Pendeen Area
    • Botallack, and Botallack Mine
• Canada
  • Quebec
    • Rouville County
    • Mont-Saint-Hilaire
  • Interior British Columbia
• United States
  • California
    • Inyo County
  • Nevada
    • Churchill County (Soda Lake District)
    • Humboldt County
    • Mineral County
  • Oregon
    • Lake County
  • Pennsylvania
    • Karns
    • Natrona
  • Washington
    • Okanogan County
  • Wyoming
    • Natrona County