corundum, sapphire, Nigeria.12, Brazil.12, inclusions.5, gems

Henn describes blue sapphires from two then relatively little-known localities, Nigeria and Santa Terezinha de Goiás, Brazil, comparing their appearance, physical properties and characteristic inclusions. The Nigerian material, reportedly from about 50 km north of Jos, is typically dark to inky blue with pronounced color zoning. Microscopic features include fluid and elongated two-phase inclusions, idiomorphic apatite crystals and rounded zircon crystals. The Brazilian sapphires are generally of poor transparency and bluish gray color, sometimes showing strong dark-blue zoning; characteristic inclusions include muscovite and margarite oriented along cleavage directions. The study provides preliminary diagnostic information for distinguishing sapphires from these two sources.