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Setting pyritized ammonite


#1

Question: I have a perfect little pyritized ammonite all ready for
setting in a ring or a pendant. Will it need a protective coating
,or is the pyrite tough enough to maintain its finish when worn?
Dee


#2

Hello Dee! As I recall this material is not very tough. It chips,
(flakes) rather easily. I would hazard aguess at a hardness of 4 to
4.5 Mohs. I worked with two pieces for a designer in the late 80’s
who was in turn selling them in Japan. It was very popular over there
then. The durability was a known deterrent to ring wear, however. I
would assume only occasional wear, if left unprotected. I can’t
imagine it looking too great with a quartz or spinel cap laminated
over the top. Yes they do that with them. An oil painting doesn’t
look to good covered with a sheet of glass to my eye either.
Hopefully someone has your answer, that may protect it, and not
cheapen its’ appearrance. Tim


#3

Also, I might add – while I am not that familiar with pyritized
ammonite, I know that pyrite itself does darken in time, when exposed
to air. Perhaps it would be wise to cover it (i.e. seal it) with
something in order to prevent this darkening. but I have no particular
suggestions as to what. Perhaps the source you got it from might have
suggestions? Margaret


#4

Dee, pyrite is sulfur and iron, almost a recipe for oxidation.
Exposure to air will cause it to soon begin changing color.
Additionally, it is likely to be fragile. Used in a ring, the ammonite
would probably break soon, possibly while trying to set it (this from
personal experience setting one for a pendant). The better you seal
the entire ammonite the longer the finish will last.

As gratuitous overkill, the pyrite ammonites are coming from
Mikhailov, Russia. Their age is Middle Jurassic, Upper Callovian and
the species noted from there by Jim Wyatt, owner of fossilnet.com, are
Binatisphinictes rjazanensis, Cosmoceras compressum, C. proniae and
Rondiceras chefkini.

Now aren’t you sorry you asked?

John McLaughlin
Glendale, Arizona
@John_McLaughlin


#5

Hello- on the setting of pyrite… I did some pieces a few years ago
with regular cut pyrite (not pyritized anything). It had the strange
property of not only darkening itself, but turning all the silver
around it black! I don’t know if anyone else has had this problem.
The setting was not a very wide area, but it turned black within a
few weeks. I would polish it up, and it would blacken again. This was
not just one piece- I had made about ten. I theorized that something
in the pyrite was either out-gassing, or somehow was attracting
elements in the atmosphere that would accelerate tarnish. I’m not a
mineralogist- I just stopped using pyrite. There were small gold
elements in the design that were unaffected. I’d love to use it
again- I bought some beautiful pieces of pyrite before I discovered
this problem. Before you set any, maybe someone on Orchid who knows
more can tell you if this is a common problem, and if there is anyway
to overcome it. -Lin


#6

I suspect that when pyrite darkens that the chemical reaction is
giving off sulfur dioxide. At least there is a similar reaction with
its close relative, marcasite. Marcasite really should not be put in
the same container with silver, lest the silver darken. It might be
good to look into this further if you are considering using silver in
your design. Just a thought. Rose Alene McArthur


#7

Pyrite plus the water in the atmosphere produces sulfuric acid which
oxidized (darkens) the silver. I do wonder if a coat of varnish
would stop it ? ? ?

thanks for being here
gregor


#8

After all the discouraging words about setting pyritized ammonites,
I’ve decided to do it in wax and cast it in brass or silver . Then I
can make rings, earrings or whatever I choose without losing either
the look or the stone. Along the way I also learned that you can
restore the sheen of the pyrite surface by brass-brushing it when it
darkens. So I’ll just save the original and thank all of you for your sound advice.
Dee


#9

Hi all, This is a bit of a cheat, but offers many interesting
possibilities. I have had pyritized ammonites molded and cast with
mixed results, but when the results are good, I have a sterling silver
ammonite replica which can be used directly, soldered in place etc.
Unlike the real thing, the replica is not too fragile and does not
have any of the problems associated with using sulphide compounds in jewelry. MP