Diamond Gemology

Natural colors

Artificially colored

All hues

All hues, gold-yellow to amber colors,

often very "oily" appearance

Yellow line 415.5 clear,

Lines at 498, 504, 594 nm

other lines of the

plus lines of the yellow series

yellow spectrum weaker

All hues

a) Brownish to purple

b) Yellow-brown to deep brown

Clear line at 504 nrn,

a) Diagnostic: 594 nm clear

accompanied by a weaker

weaker lines at 637,620,

double line at

610 nm and possibly yellow line

498 and 537 nm

b) Equal strength double line at

498 and 504 nm and possible yellow

line

Very rare

Umbrella effect or dark ring

in the girdle

.

Line at 504 nm clear,

Pair of lines at 498 and 504 nm

498 nm weaker or not

of equal strength and possibly

present at all

yellow line

Type II b, electrical

Type I a, no electrical

semi-conductor

conductivity