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This list digest contains the following message subjects:

1. LapDigest News for Issue No. 41 Thursday 8/7/97
2. CONTEST: 'You Know You're a Rockhound When...' Contest
3. NEW: Polishing Tiger Eye
4. NEW: Polishing Rainbow Obsidian
5. NEW: Polishing Labradorite


Subject: LapDigest News for Issue No. 41 Thursday 8/7/97

Well, it seems we are back to basic Lapidary, today, having three questions about polishing various materials, and a contest. No 'twilight compass' minerals from Norway, just basic lapidary items.

I would like to hear from any of you with experience in vibrating lapping machines - just tell me what kind of machine(s) you have, and what material you polish. Let's do a whole issue on "how to use a vibrating lap". Among the 315+ members must be lots of members with experience in this whom we can draw on for help.

Also if you have vibrating lap questions, please send them in; I will try to make sure they are answered in the vibrating lap issue.

Finally, I am making two changes today. First is a new version of the software. Next - for all of you who are experiencing trouble printing out the Digest, please try printing this one out and look at the printing of the third item: "polishing tiger eye". How does this one item print out?


Subject: CONTEST: 'You Know You're a Rockhound When...' Contest

Greetings to the Lapidary List,

I've just launched a monthly contest at Bob's Rock Shop for
"You Know You're a Rockhound When..." type one-liners,
extending the longstanding "Some Surefire Signs You're a
Rockhound" feature at the Shop.

The 1st place winner of the current contest will have the
pick of a copper after aragonite psuedomorph, or a year's
subscription to Rock&Gem magazine. Second place gets the

I plan to run this contest on a repetitive basis for as
long as interest and participation warrants, and if it
proves to be a popular contest, I'll increase the depth
of the places and prize pool.

You're all welcome to come share some rockhound humor.

Bob Keller

Subject: NEW: Polishing Tiger Eye

One of my favorite stones is tiger eye, so it was an
early choice when I started to learn lapidary last year.
I've polished several shapes over that time but have not
been pleased with the surface finish I get.

I rough shape on hard diamond wheels at 80 and 100 grit
as needed, final shape on a 220 hard diamond wheel, and
then sand with corrundum belts at 100, 220, 400 and 600.
Polishing is with cerium oxide on rough leather. I've
tried light polishing with lots of water and forceful
polishing until the cerium's almost dry and pulling on
the stone. After sanding there always seems to be some
area of tearing of the fibers on the surface of the cab
when viewed under 10x. These voids fill with the cerium,
and I've never been able to get the surface clean

Alternatively, I tried diamond polishing after the 600
grit sanding. I started with 600, then proceeded to 1200,
8000, 14,000 and 50,000. The results are better, but
there are still some pits in the surface under 10x.
Also, I'm concerned that the diamond polishing may not
hold up over time. The surface may look better just because
there's no cerium in the pits, but other crud will
eventually get in them and destroy what finish I have.
Another reason might be that the diamond grit is suspended
in a Crystalite oil base which may be filling in some of
the smaller pits making the surface appear better that it
really is.

The bottom line is that I've not yet been able to get as
nice and as even a polish as I've seen on tumbled tiger
eye or on cabs I've seen at Federation shows.

What's the secret, guys ?

- Brad

Subject: NEW: Polishing Rainbow Obsidian

I am looking for some help from other members who may have had some
experience polishing rainbow obsidian. I have tried shaping free-form
pendants first with an 80 grit diamond wheel, and then shaping them with
nova wheels 200 grit through 600 grit. I continue polishing with nova wheels
1200, 14,000 and 50,000 grit. No matter how careful I am at each step, when
I get to the final polishing stages I find that there are tiny depressions
or spalls on the surface that remain dull. I have even tried starting the
rough shaping process with a worn 600 grit silicon carbide belt, but I
still end up with the same results. Can anyone help me?

Non-commercial republish permission granted

Subject: NEW: Polishing Labradorite

I would also like some advice on polishing labradorite to a beautiful
finish like the specimens currently coming out of Madagascar. I have tried
using all the nova wheels through 50,000 and the finish is fair at best.
The pieces coming out of Madagascar look like the finish is "melted",
almost as if the pieces were polished using a compound at a high speed or
temperature. Has anyone had any experience with this material?

Non-commercial republish permission granted
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