Fingerprints. The inclusions with a descriptive, poetic name, are common in Corundum (sapphires and rubies.) They resemble pieces and parts of a human fingerprint and float inside the stone. Fingerprints are actually fluid-filled inclusions or natural internal healing patterns from the crystal’s growth. When sapphires are heat-treated, much of the fingerprint dissolves and is no longer visible. Therefore, the presence of fingerprints is a good indicator that the stone has not been heat-treated. Depending on where they are located and how dense the group of pinpoints, we might be able to see fingerprints with our eye, however, fingerprints are much easier to spot with a loupe or microscope and good lighting. That’s what you have me for. Fingerprints are beautiful, delicate, lacy patterns and nothing to fear.