onyx

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Art Déco Era men's cufflinks and shirt stud set with black onyx & diamonds

Variety:  Onyx
Species:  Chalcedony
Mohs Hardness:  5 to 6 out of 10
Color:  Banded variety of chalcedony that has alternating bands of white and various colors such as black, red and green
RI:  1.535 to 1.539 (1.53 to 1.54 spot reading)
Birefringence:  Usually not detectable
SR/DR/AGG:  AGG
Spectrum:  Not diagnostic
Fluorescence:  Generally inert
SG:  2.60 (+0.10/-0.05)
Routine Treatments:  Dyeing

onyx facts

Large black onyx pendant

Onyx is a variety of chalcedony with parallel color banding that occurs in white and nearly every color except blue and purple.

Onyx has parallel color banding while agate's bands can be much more chaotic.

​Black onyx rarely occurs in nature, but is often dyed to achieve its deep black hue.

Onyx Gallery

All photos courtesy of Scott Papper, GIA GG, AJP, CMA (NAJA)