I seem to remember that it was found in the British Isles and
places on the continent, the latter of which surprised me at the
time. I wonder where the garnets were coming from - chances are,
the style radiated outward from there.
Tas and others, I don’t post much any more but maybe I can help out
on this one. The Romans loved garnets in all their wonderful variety
and used them mainly as decorative cabochons in medallions. They had
many sources for fine garnet throughout the Empire including Bohemia
and points throughout the Middle East.
In the late Roman period a new garnet jewelry tradition emerged,
apparently beginning in south Russia. It consisted of flat-cut
garnets polished on both sides and mounted in gold cloissons
(frameworks). These were at first glued in place but during the
so-called Dark Ages many European kings retained the finest
goldsmiths available and garnet cloissone jewelry became something
of an art form. (It’s definitely cloissone even though today the
term is used almost exclusively for cloissons filled with enamel
instead of real gem stones).
The Sutton Hoo treasure, dating from the 7th century, features what
is considered the finest garnet cloissone known. It came from an
Anglo Saxon king’s funerary ship burial in East Anglia discovered in
1939. It yielded 45 pieces of jewelry that incorporates about 4,000
garnets individually cut and polished to fit exactly into the
cloissons – no glue is used. They are held only by the precision of
the fit. The creators also understood the "dark garnet problem"
known very well to modern day gem cutters. Some garnets have such
deeply saturated color they’re attractive only in transmitted, not
reflected light. For that reason the goldsmiths used polished gold
foil at the bottom of the settings to mirror light back through the
thinly-cut stones, yielding a fine red. Gem-grade garnets today, of
course, are cut from select and scarce lighter-hued gem material.
I’ve seen this collection at the British Museum and it is humbling
to realize such fine work was accomplished with what today we would
consider primitive tools. Some of the stones are under 1 mm. in
diameter and intricately shaped. Experts on the subject say this
jewelry tradition died with the owner of the Sutton Hoo trove in 622
A.D. No more of its type has been found.