Pronunciation

bye-AKS-ee-uhl POZ-i-tiv

An optical character of anisotropic gemstones where light travels at three distinct refractive indices (nα < nβ < nγ) along three principal optical directions, with two optical axes along which light behaves isotropically. "Positive" indicates that the intermediate index nβ is closer in value to nα than to nγ. Diaspore is biaxial positive; this is a primary diagnostic feature.