Sapphires were found during road construction after exposure of a monchiquite dike, traced for 25m with a thickness varying from 0.5m to 1.5m.
Sapphire crystals have hexagonal, pyramidal-dipyramidal or bladed habit with an average size of 2 to 3cm. Smaller crystals are pure blue, larger stones are spotty blue and green with occasional yellow patches. The indices of refraction are 1.762 - 1.775 and the density is 3.95 - 4.05 g/cm³ (Jackson, 1984).
Ref: E.Ya. Kievlenko (2003) Geology of gems, p. 48