LAPIDARY DIGEST
Administered by Hale Sweeny (hale2@mindspring.com)
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This list digest contains the following message subjects:

1. LapDigest News for Issue No. 159 - Wed 7/22/98
2. NEW: Collecting in North Dakota
3. NEW: Orienting Jade for Polishing
4. RE: About Charoite
5. RE: About Charoite
6. RE: About Charoite
7. RE: About Charoite
8. RE: About Charoite
9. RE: About Charoite
10. RE: Tumble Finishing Cabs
11. RE: Tumble Finishing Cabs
12. RE: Tumble Finishing Cabs
13. RE: Tumble Finishing Cabs
14. RE: Tumble Finishing Cabs
15. BIO: Michael & Susan Hustad


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<MSG1>

Subject: LapDigest News for Issue No. 159 - Wed 7/22/98

I am off to the Gem Shows at Franklin and Spruce Pine, NC,
and will return on July 27, so the next issue will be about
then!

Also, in the last issue, I said: "...this coming weekend,
August 28,...". I wrote that at about midnight and it is
obvious that I was tired and sleepy.

Take care of yourselves, and have FUN!!

hale
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<MSG2>

Subject: NEW: Collecting in North Dakota

(This was originally part of the Bio published below.)

We are going to visit family in Minot, North Dakota and since
we will be flying, we'll have no car for long trips. But is
there anyone that has knowledge of any mining areas around
there that we could enjoy while visiting???

Susan
sueboltfan@aol.com
"non-commercial republish permission granted"
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<MSG3>

Subject: NEW: Orienting Jade for Polishing


I picked up a piece of jade at the silent auction of a rock
show recently. One end is cut off, and the cut surface has
some white areas that seem to reflect the state of the
internal structure. Not that the stone is white there, the
cutting has almost a frosted surface to it. This is probably
a pretty vague way to describe it, but I am doing the best I
can.

I know that jade will polish differently depending on the way
it is cut, and my intuition tells me this may not be the right
angle of a cut for polishing. But is there any way that you
can determine the optimal direction without cutting and
polishing three sides to observe the difference?

Thank you,
Rose McArthur
<obmcarthur@clearwater.net>

- non commercial republishing rights granted -
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<MSG4>

Subject: RE: About Charoite

As I cabbed the material, one problem that I experienced
involved the fibrous nature of the material. It seems to
split along the swirls almost as cotton candy would. Also,
the often rather large included minerals offered a small
problem with undercutting.

Best of luck,
EMJ - The Duke of Dubuque
<EMJRKS@aol.com>
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<MSG5>

Subject: RE: About Charoite

Hale;

Charoite needs to be handled very carefully. It doesn't like
rough grinding and will chip and flake easily. Baby it along
and the results will be gorgeous. New Era Gems usually has
some available (at their usual!! prices).

Paul H. Miller
<kabal@ctaz.com>
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<MSG6>

Subject: RE: About Charoite

This is a simple (make that stupid) question: I pronounce it
as SHAR'-O-ITE, with a little added stress on the 'shar' part.
Is this the proper pronunciation of the word? (It is not in
my dictionary!)

hale
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<MSG7>

Subject: RE: About Charoite


I've had extremely bad luck with Charoite. Glad I traded for
it and didn't pay what most dealers are asking for it. Some
on this list will undoubtedly disagree, but my experience has
been that even on a Titan, w/ soft diamond wheels and plenty
of water, it will expand and flake apart more often than not.

If you can get it to stay together through the polish you're
a better lapidary than me! (I know it can be done; it just is
not a suitable material for most amateur lapidaries, IMHO).

Tim Fisher
<tim@orerockon.com>

non-commercial republish permission granted
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<MSG8>

Subject: RE: About Charoite

Charoite:

I have cut 30 or so cabs and love the stuff. Some tips are as
follows:

1- Use light hand pressure.

2- Start rough cutting with a 260 diamond wheel or finer grit.
(The stuff is almost fibrous in places and the edges can
be a real pain.)

3- Chamfer or a slight rounding of the bottom edge helps keep
the stone from peeling away.

4- It is a little heat sensitive so use plenty of water. It
has a tendency to grab the wheel.

5- Softer areas will undercut, I have found that a well worn
600 belt helps out here.

6- Polishes up well with Cerium on leather (wet), but haven't
tried anything else so playing with other types of polish
may be as good or better.

BTW, even the stuff considered Second Grade Rough can turn some
really neat stones so don't let the Top Grade Hype fool you
into passing up some wonderful material at a cheaper price.
IMHO

Hope this is of some help.

Craig Nielson
<cnielson@webtv.net>

"non-commercial Republish Permission Granted"
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<MSG9>

Subject: RE: About Charoite

As Hale mentioned, Charoite is calcium potassium silicate.
Other minerals present are; black: Augerine Augite,
transparent crystals: Microcline Feldspar, and orange:
Tinaksite.

I have not found it to be very heat sensitive. I hot dop it
and put it in the freezer to remove it with no problems yet
(I have only cut a few hundred stones so I may change my mind
later).

What I have found is that the white banding between the purple
is softer and subject to fracture. This usually occurs when
grinding but I have had it happen during sanding, only rarely
during polishing. If it has held together long enough to get
to the polishing stage I am usually OK. I do my preforming on
a fine grinder (380 grit) with a light touch and hope for the
best.

I have read that Charoite can only be worked with diamond but
I have not found it to be true. I find I get the best results
treating it like jade. After sanding through 1200 grit, (with
diamond but I don't think the stone cares) I dry sand it with
1200 grit silicon carbide and polish with aluminum oxide. I
find it easier to control the under cutting with SiC than
diamond but I know others prefer diamond. If you have a
technique that controls stones that undercut during sanding I
think it will work with Charoite.

I have used cerium oxide, diamond, and aluminum oxide to
polish Charoite and all three worked. I just like aluminum
oxide better. Aluminum oxide is available in a variety of
grits, is covenant to use, 9 hardness, and is cheap. I like
a two step polishing process. I like to start with 1.0 to .35
micron and finish with 0.2 or 0.1 micron. This is roughly
equivalent to 50,000 and 100,000 diamond and I think works
just as well for stones under a 9.0 hardness.

Cerium oxide is the polish of choice for the glass polishing
industry because it can be formulated for the different
processes they need. From the lapidary standpoint it is hard
to find out which process it was designed for, they are all
"optical grade." If you are having good luck with your cerium
oxide, stay with it. If you are having problems, try a
different source, you may have better luck.


Dick Friesen
<friesenr@ix.netcom.com>
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Subject: RE: Tumble Finishing Cabs


Recently I experimented with tumble finishing cabs. I first
preformed each cab on the 100 and 220 grinding wheels. I
used a small lot of cabs and added enough softer material to
fill a very small barrel to the proper level for tumbling
action. I tumbled just enough time in 400 grit to remove any
scratches.

I was disappointed in the results from this first step of the
first batch. A good portion of the cabs had lost just enough
of their original shape to where I would no longer consider
them useable. Even with minimum tumbling time at 400 grit,
any soft spot or imperfection in the cab was magnified by the
tumbling action - especially around the thinner bezel area.
I had ground the cabs just oversize enough to where the
finished tumbled size was still good, but some of the stones
had lost that "perfect cab" look. I didn't even bother
polishing them and ended up re-grinding them smaller and
finishing them by hand.

Before I tried my experiment, I read where a few of other
people had tried tumble finishing cabs and had better luck.
That's what inspired me to try it, but now I don't think I'd
waste the time again. After finding and reading a couple of
more stories about it, I've gotten the impression that tumble
finishing cabs is only good for the polishing stage. With
proper grinding and sanding, polishing should be the quickest
part of cab making. So, to me it really wouldn't be buying
me much, unless the quantities were large enough to justify
doing it. I know the commercial cab producers do it, but I'm
sure they have the material, equipment, and economy of scale
to make it a profitable process.

Jim Schnell
<SchneDJ@Louisville.Stortek.COM>

noncommercial republish permission granted
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<MSG11>

Subject: RE: Tumble Finishing Cabs


Steve and/or Terrah,

I have had some experience in tumble finishing cabs. Many
times, I find myself wondering why I keep working on a
certain cab: It may be not as nice of material as I thought
it was when I started. Or I just get bored with it or
whatever. For these stones, I keep a few plastic containers
near my bench that I sort them into according to
hardness/toughness. When I accumulate enough of them for a
tumbler load, in they go!

As far as how much you need to do prior to tumbling: the main
thing is to have them the right shape. Any bumps, ridges or
flat spots aren't goint to magically disappear in the tumbler
(though they will be somewhat diminished). I have tumbled
stones straight from my 100 grit grinding wheel. I have
three rotary tumblers of various sizes and one small vibratory
tumbler. I highly recommend going with vibratory, as its
easier to check their progress regularly. I usually start
with a relatively short run of 220 grit, followed by regular
prepolish and polish stages.

Some things to consider:

Keep in mind that everything is gonna get smaller in the
tumbler. If you're trying to do a calibrated stone, you have
to allow for the shrinkage.

Anyone who even has a little experience in this biz can tell

at a glance that it is a tumble polished stone, unless it is
hidden in a good bezel setting (I only use this procedure for
stones I don't care much about, and they usually end up as
gifts for my kids or nieces and nephews).

Make sure you get ALL of the dop wax and/or glue off the
stone, before starting (my first batch had weird little bumps
on the bottoms, shaped curiously like a dop wax ring).

I'm sure there is much more I could tell you, but I haven't
done a batch like this for a while, and my brain doesn't work
as well as it used to. I have met people who do all of their
cabbing this way. As for me: Nothing beats a well shaped and
polished cab done by hand. Call me a purist (snob?).

Mark Williams,
In sunny, humid Oregon
<stnbrk@rio.com>

non-commercial republish permission granted
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<MSG12>

Subject: RE: Tumble Finishing Cabs


Works great, but beware that you'll get a "wavy" appearance to
the cab if you start with 100/220 in the tumbler and the
material is not of perfectly uniform hardness (most agate and
jasper with the exception of most picture jaspers is not of
perfectly uniform hardness).

Vibratory tumblers work great for this; rotaries do not. It's
tough not to chip your cabs in a rotary; they rarely chip in a
vibratory. High domed cabs hold up better than flatter ones;
rounds and ovals polish better than odd shapes. IMO if you're
going to start with 500F in the tumbler then you might as well
go the distance on diamond. If you don't have diamond then it
makes sense to go to a vibratory.

Tim Fisher
<tim@orerockon.com>

non-commercial republish permission granted
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<MSG13>

Subject: RE: Tumble Finishing Cabs


Steve and Terrah Swartz wanted to know about polishing cabs
in a tumbler. I have polished cabs in my mini sonic tumbler
as well as my larger vibrating tumbler. The rotary style
tumbler ends up breaking too many cabs so I do not use it for
cabs.

Basically what I do is shape the cabs and get them ready to
polish with progressively finer grades of grits down to about
400 grit. Then I put them in the tumbler with 400 for a few
days, and then 600 grit for the pre polish. The better the
pre polish the better the polish -- then I polish. I run them
for three to five days on each grade of grit, and if I don't
get a good polish I go back to 600 and pre polish again. It
works for me. It saves quite a bit of time.

You can't just rough the cabs out though because you will not
be happy with the results. The cabs have to be ready to polish
or pre polish. If you throw the cabs into the tumbler when
they have just been roughed out you will have to go through
all the different grades of grit and you will lose too much
size. You won't be able to control the final size of the cab.
I like to have a good idea what size the finished cab will be
when starting out. Anyway fiddle around with it. You will be
pleased with the results.

Dixie Reale
<dixietr@magiclink.com>
http://www.dopplerfx.com/kounting
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Subject: RE: Tumble Finishing Cabs


As a neophyte to lapidary, I gathered bunches of ancient
magazines and in one was an article entitled something like
"Prizewinning Cabber Tells His Secrets."

First, do NOT use a rotary tumbler. You must use a vibratory
tumbler only. Layer the stones no more than 3 deep with drier
lint, replacing the lint between pre- and final polish.

The 200 grit sanding sounds way too course to me. 600 would
seem a better choice.

He warned that some will not take a good polish no matter what
you do and you may have to go to hand polishing with those,
but the majority should take an eye-popping shine.

Jerry Mings aka Rich Balding
<wizard@net-quest.com>
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Subject: BIO: Michael & Susan Hustad

Hi,
We are fairly new to this news group and have enjoyed reading
and learning from everyone. I have loved rocks all of my
life and drug my family into it as well, so much so, that 2-3
years ago, we started buying old lapidary equipment to turn
my mountains of rocks into beautiful cabs. Mainly, this has
been for our own enjoyment and a few family presents.Southern
California has some nice material to work with and now I have
a good excuse for browsing the rock beds where ever we go!!


Susan
sueboltfan@aol.com
"non-commercial republish permission granted"
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