Zigzag Fingerprint in Sri Lankan Sapphire
The rectilinear zigzag-patterned fingerprint in this 3.21 ct blue sapphire shows beautiful vibrant colors, indicating a Sri Lankan origin. Photomicrograph by Yuxiao Li; field of view 4.45 mm.
The author recently examined a 3.21 ct oval mixed-cut blue sapphire. Chemical analysis and gemological observation of internal fissures suggested a Sri Lankan origin. Under fiber-optic illumination, the fingerprints showed rectilinear zigzag-patterned films with vibrant colors that resulted from thin-film interference (see above). The rectilinear structure of this fingerprint was caused by the natural healing process of a fracture oriented parallel to the c-axis.
These zigzag-patterned fingerprints often indicate a Sri Lankan origin, but they can also be found in sapphires from Myanmar and Madagascar. The undamaged rectilinear pattern could indicate that the stone is unheated.
