Darker edge/“rim” on garnet chips

[Pinkmartini87]

Hi, curious why this pair of garnet chip earrings appear have a darker border (is it due to a variation in thickness from center to periphery?)

Ted Muehling - 18k Gold Top Garnet Chip Earrings

Chip earrings with hand-cut garnet with 18k yellow gold ear wires. Measurements: Garnet Chips with 18k tops measure 3/4” x 1/2” Hanging the earrings measure approx. 1 1/2" from top of ear wire to the bottom of earring Ted Muehling has been designing jewellery and decorative objects in his NYC...

moukimou.com

 

[Autumn in New England]

Hi, curious why this pair of garnet chip earrings appear have a darker border (is it due to a variation in thickness from center to periphery?)

Ted Muehling - 18k Gold Top Garnet Chip Earrings

Chip earrings with hand-cut garnet with 18k yellow gold ear wires. Measurements: Garnet Chips with 18k tops measure 3/4” x 1/2” Hanging the earrings measure approx. 1 1/2" from top of ear wire to the bottom of earring Ted Muehling has been designing jewellery and decorative objects in his NYC...

moukimou.com

It just looks like a function of the cut to me... convex with thin edges and a thicker center on both sides.

 

[Pinkmartini87]

It just looks like a function of the cut to me... convex with thin edges and a thicker center on both sides.

Many thanks as always for your help!

This may be a stupid question then so forgive me: shouldn’t the color be darker where the depth is thicker, whereas a thinner portion lets in more light? Ie if the convex shape means the center is fuller/thicker, shouldn’t the more shallow edges be lighter?

 

[Starstruck8]

I think it's the cab version of a window.

If you ray-trace from the eye (a bit counter-intuitive, but easier to explain), rays in the middle parts are not deviated much, so they can partially pass through the back of the cab. So you can see some light from the white screen behind the stone. The cab is quite thin, so with the short path length, there's not much absorption. But rays near the edge of the stone are deviated so much that they are totally reflected from the back to the other side of the stone. This is a longer path (about the width/length of the stone), so there is strong absorption.

Here's an example I grabbed from the net:

 

[Autumn in New England]

Many thanks as always for your help!

This may be a stupid question then so forgive me: shouldn’t the color be darker where the depth is thicker, whereas a thinner portion lets in more light? Ie if the convex shape means the center is fuller/thicker, shouldn’t the more shallow edges be lighter?

@Starstruck8 answered it better than I could!

 

[Pinkmartini87]

@Starstruck8 & @Autumn in New England Many thanks—makes perfect sense now!