Gold

Formula: Au

Reflected/transmitted colour: opaque in all but the thinnest flakes, then blue and green, polished section bright or 'golden' yellow, varying with the content of admixed metals

Pleochroism:

Optical isotropy/anisotropy: polished section isotropic, no complete extinction under crossed nicols, but typical greenish tints

Optical sign:

Refractive indices:

Birefringence δ/bireflectance: in polished section not present

2V angle:

Dispersion:

Optical orientation:

Optical axial plane:

Light grayish grain of intimately intergrown isomertieite and arsenopalladinite (in the center of the picture), with pale yellow gold and brownish to violet bornite. Polished section (from microprobe analysis) in reflected light.

Origin: Noril'sk, Putoran Mts, Taymyrskiy Autonomous Okrug, Eastern-Siberian Region, Russia

Picture size: 0.1 mm

Owner: Thomas Witzke

 

Photo courtesy of: