Detrital mineral morphology and geochemistry: Methods to characterize and constrain the origin of the Nsanaragati blue sapphires, south-western region of Cameroon

► Nasanaragati alluvial blue sapphires are characterized to constrain their sources. ► Grain shapes suggest magmatic corrosion and distal transport of crystals. ► Trace element values suggest they originally crystallized from Al-rich alkaline magmas. ► Subordinate sapphires are Ti-enriched, suggesting that more than one source was tapped. ► The sapphire grains are typical of basalt-derived xenocrysts found in placers.