Fire opal question

Jewelry Discussion
1

Hi,

was wondering if fire opals always go opaque in sunlight? or am I
mistaken about the type of stones I have? Anyone else have this
experience?

Related Readings:

[Ganoksin] - Lets Talk Gemstones - Opal 
http://www.ganoksin.com/borisat/nenam/opal.htm

[Ganoksin] - Lets Talk Gemstones - Opal Part 2 
http://www.ganoksin.com/borisat/nenam/opal-1.htm

thanks!
peggy

2

Hi Peggy,

First let’s make sure we’re talking about the same thing. I’m taking
fire opal to mean the reddish to honey colored transparent to
translucent opals which may or may not have play of color that
typically come from Mexico although there are other locations.

To answer your question no they don’t always go opaque in sunlight.
But some do. In my own experience these are a minority. I had one
nice approx 3 carat step cut Mexican which after a year had
developed a cloudy white patch with a crescent-shaped crack around
it. Many, indeed most, others have stayed stable for years.

A recommended practice for Mexican and other susceptible opal is to
leave the rough out in the sun for six months or a year. If it
hasn’t altered after that, it probably won’t. Probably is the key
word. There are no absolutes but it’s a reasonably safe bet.

Cheers
Hans Durstling
Moncton, Canada

3 
   was wondering if fire opals always go opaque in sunlight? or am
I mistaken about the type of stones I have? Anyone else have this
experience?

While the type of lighting hitting a stone may change the way it
looks, it seldom changes the actual optical properties of the stone.
I don’t think I’ve ever seen an opal of any kind that changed it’s
degree of transparency in sunlight versus some other light source.
Differing light sources may change apparent intensities of colors,
and stones may appear radically different when lit from behind
instead of from the front, or with diffuse light instead of a point
source like sunlight. But the opacity/transparency? That shouldn’t
change. What does your stone look like?

4

I’ve owned/own quite a lot of Mexican fire opal and wore a number of
them. Have owned all for over 20 years and none have clouded over or
changed in any way. My vision-impaired husband loves them best
because he can actually see that color clearly. Least I can do, huh
? On the other hand, a hand-carved wooden pendant - walnut I recall -
scared me to death one day in the sun in Mexico when it split with a
gunshot report on my chest. Just couldn’t take that hot sun of
Yucatan.

I hunted the nearest cooling cafe to chill Me out. Love those
opals.

Pat

5 
While the type of lighting hitting a stone may change the way it
looks, it seldom changes the actual optical properties of the
stone. I don't think I've ever seen an opal of any kind that
changed it's degree of transparency in sunlight versus some other
light source.

How about Kunzite becoming cloudy?.. The ‘Night Stone’ a it is
referred to because it can become cloudy after a couple of years?

Jimc

6

“Night Stones” are usually stones that show a better color under
artificial light.