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Tumbling Moonstone


#1

Hi All: Can finished Moonstone earrings be tumbled in a small,
rotary tumbler without incurring damage to the stones? According to
the Mohs Scale, they are feldspar and have a hardness of 6–as does
opal and turquoise, so I wondered if they may be too soft.

A few weeks ago I received a bunch of wonderful responses to my
query about giving the moonstones a bluish cast. I finally settled
on some hard plastic cut from a pair of old kitchen measuring spoons
that were exactly the right color. Thanks to everyone who responded. Sandra


#2
    Hi All: Can finished Moonstone earrings be tumbled in a small,
rotary tumbler without incurring damage to the stones Sandra 

I wouldn’t recommend it, since the moonstones are likely to be
bumping into each other, and having the same hardness, they can
abrade each other. If you really need to do this, consider painting
them with a couple coats of nail polish and wiring them to a metal or
plastic rod so that they can tumble without contacting each other.
I’m assuming you are planning to tumble them in steel shot. Also,
even a material that is softer than a stone can damage that stone if
it strikes it either with enough force or finds a tiny opening in the
surface of the stone. I have scratched rubies and saphires while
burnishing a bezel because there were surface blemishes too small to
see but small enough to provide a place for the tool to crumble off a
little material. Might I suggest using the small steel end brushes
and steel rotary brushes in your flexible shaft tool? Steel shot
isn’t going to be much more effective than those steel brushes in
tiny little cavities. For that kind of burnishing, you need a
magnetic tumbler with pins.

David L. Huffman


#3
    Hi All: Can finished Moonstone earrings be tumbled in a small,
rotary tumbler without incurring damage to the stones?  According
to the Mohs Scale, they are feldspar and have a hardness of 6--as
does opal and turquoise, so I wondered if they may be too soft. 

Sandra - don’t do it. Think about putting your finished jewelry in a
can with a bunch of heavy rocks or steel shot, then shake the stuff
for a couple of hours. It might work, but why not wait until you
finish the metal in a tumbler, then set the stones?

The only time I think it is safe to run most gemstones in a tumbler
is in sawdust for final polish, and then only with hard non porous
stones.

Judy Hoch


#4

Hi Sandra,

I’d like to follow up on what Judy Hoch had to say in her reply to
you, yesterday. Not only shouldn’t you consider tumbling your
Moonstone earrings in a tumbler, but you’d probably be wise to avoid
tumbling most gem materials, once they’re set. My reason for
suggesting this is that nearly all transparent gem materials are so
extremely brittle that the impact of a body of metal into them could
easily damage them, and the vast majority of those other than
Diamond, Topaz, Kunzite and the Corundums are able to be scratched
quite easily (like, by the abrasives caught between two pieces of
jewelry inside the tumbler’s barrel).

In addition to these factors, you need to be wary of one of the
properties of all Feldspar gems, be they Adularia (Moonstone),
Amazonite, Labradorite/Spectrolite, Sunstone or others: in all
cases, Feldspar has two perfect cleavage planes, one of which is
very easily developed by even a casual knock. Toss one of them into
your tumbler long enough to facilitate a good polish on the silver,
and you’ll more than likely cause some of these cleavage planes to
open up – not necessarily to the point of risking the stone’s
survival, but easily enough to dull the finish, enough to warrant
sending it to a lapidary shop, like mine. (Not that I’d turn away
your business, mind you; just that you probably could do without
that kind of a headache.)

While we’re at it, be careful when using Tripoli near Moonstone or
Labradorite, too: it’s harder than they are, and a brushful of it
can undercut your stone while it prepolishes your mountings,
simultaneously. (I’m not suggesting you not use the stuff, just keep
the comparative hardnesses in mind, when you use it.) Hope I’ve
helped, more than hurt!

All my best,
Douglas Turet, GJ
Another Bright Idea! / Turet Design
P.O. Box 162
Arlington, MA 02476
Tel. (617) 325-5328
eFax (928) 222-0815
anotherbrightidea@hotmail.com


#5

All, There may be a bit of misunderstanding here.

If the question is (and I believe it is) can moonstones already set
into ear rings be tumbled in steel shot?

The answer is not a super good idea simply because the shot has many
shapes to it including sharp points and edges. But, the shot is
probably only a 5 to 5.5 on the hardness scale whilst moonstone is a
6 to 6.5 whether albite, oligoclase or sanidine. Thus, the shot
should NOT scratch or damage the stone, except as Dave says the sharp
points and edges may find a tiny opening and ‘pry’ into it. The
metalic residue would probably be more damaging to the stone if it
could find its way into any microscopic pits, hollows, etc.

Moonstone tumbles very well by its self in grit and polish. It can
be made smooth and beautifully polished in either rotating or
vibrating tumblers. I do it all the time. Like hardness has nothing
to do with abrading each other (sorry Dave) rather, when tumbling
stones, they SHOULD be of like hardness. If you want to take a chance
in shot, try a few. The result likely would be shiny metal with a
few stones showing small matte areas and some dirty flaw lines caused
by the residue. The rest should be fine!

Let us all know how it turns out. Cheers from Don at The Charles
Belle Studio in SOFL where simple elegance IS fine jewelry!
@coralnut1