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Fading agate colours


#1

Hello

Can anyone tell me why some of my coloured agate slices have faded
and others have not?

I had a small selection of coloured agate pieces that I used for
some pendants a couple of years ago. The ones I didn’t use at the
time have been kept together in a plastic tray in one of those
stacking storage boxes so they have been kept in the same conditions
away from light. They are mostly purple and a pretty turquoise/green.
Some have faded to almost gray and others have remained strongly
coloured. (I have no idea how they are coloured in the first place
but I realized they weren’t natural.) The brown and orangey coloured
pieces haven’t changed at all - I presume these are natural colours?

Can anyone advise me why some have changed and consequently how they
should be kept to avoid this?

Thanks for your help
Collette


#2

Most of the brightly colored agate from Brazil (except green) will
fade on exposure to light since the dyes they use are apparently not
light-fast.

The brown, black and gray colors are natural and are stable. The
orange carnelian-like color is produced by heat treatment and is also
stable. Dyes used in other countries may be more or less stable. I do
not know of any way to prevent this fading but blocking UV exposure
should slow it down.

Ray Prater