Edited and Published by Hale Sweeny
Web Site:
Associate Editors: Geo. Butts, JR Shroeder, Steve Henegar
and Margaret Malm

This list digest contains the following message subjects:

1. LapDigest News for Issue No 231 - Wed 9/15/1999
2. NEW: Vacuum Deposition (Was Mystic Topaz)
3. NEW: Vacuum Deposition (Was Mystic Topaz)
4. NEW: Hood For Star Diamond 10 inch Saw
5. NEW: Need Parts for Vibra-Tek Vibrating Polisher
6. RE: Tumbling Prepolish with Liquid Soap
7. RE: Motor Speed Control
8. RE: Motor Speed Control
9. RE: Motor Speed Control
10. RE: Motor Speed Control
11. BIO: James Dumar
12. Note: Newsletter from VSmithy
13. WTB: Gram Scale
14. FS: Geodes
15. FS: Mexican Apache Chrysocolla and Agate
16. SHOW: Denver Gem and Mineral Show
17. SHOW: Fort Osage Knap-in


Subject: LapDigest News for Issue No 231 - Wed 9/15/1999

Well, FLOYD is coming and the last I report I saw put Durham
right in the path of the high wind field! So we are likely
in for an exciting tomorrow! They predict winds in excess of
125 mph! If my house is still here, I'm off to the mountains
Saturday; so this is likely the last issue for a week or so.

Just take it easy and Enjoy Life!!


Subject: NEW: Vacuum Deposition (Was Mystic Topaz)

On 06 Sep 99 22:52:55 -4:00, you wrote:

<<As I understand it, in making 'aqua aura', gold or other
metals are "sputtered" onto the piece; sputtering is an
electrodeposition of some type, but I not clear about the
details of sputtering! If anyone on the list knows how
aqua-aura is made, I'd appreciate an explanation! hale>>

The process is also called vapor deposition. In a vacuum
chamber, a metal electrode is heated up, as well as being
placed on one end of a high voltage circuit. The other end
of the circuit is your specimen, or perhaps a target area
on which the specimen is placed. When the metal electrode
reaches a high enough temp, sometimes melting, sometimes
lower or higher, depending on the material, then the
voltage is enough force to cause atoms/molecules of that
electrode material to be thrown out, much like evaporation
or water with the steam condensing on the lid of the pot,
except that under the impetus of the voltage, they are
directed onto the target area which they proceed to coat.
The metal electrode must be hot. Sometimes, depending on
the material being deposited, VERY hot. Whether the target
does or not, depends on what needs to happen for the
coating to adhere. Most target materials do not need
heating of their own.

The process is widely used. In electron microscopy, for
example, samples to be viewed are gold coated this way,
since the electron microscope can only accurately image a
conductive surface. Some metalizing of things like
plastics can be done this way. For example, the chromed
plastic parts in some plastic items (including cheap plastic
toy models, for example), especially those where the
metalized layer is semitransparent for one reason or other,
can be done this way. Because it is possible to
simultaneously hook up multiple electrodes to this type of
process, and those electrodes do NOT have to be the same
materials, it is possible to deposit layers of a mixture
that might be quite hard to produce by other means.

Hope this helps.

Peter Rowe

Subject: NEW: Vacuum Deposition (Was Mystic Topaz)

In the very distant past I built and operated a machine for
vacuum deposition. Imagine a glass bell jar connected to
very powerful vacuum pumps. Firstly there was a good
mechanical pump which gave me a vacuum of less than one
millimetre of mercury pressure. But that is only useful for
sputtering, which requires a fairly high voltage arc with
the electrodes composed of the metal to be deposited.
Sputtering doesn't give quite as good a result as

At that pressure I activated a pair of large rings at a
voltage 10,000v AC. This bombarded the job with atoms of
very active oxygen which cleaned up any microscopic traces
of any organic material remaining after a very thorough
initial cleaning. In my case, the job(s) was 3 inch glass
concave lenses to be made into precise concave mirrors,
During this bombardment process, the entire bell jar glows
with a pale violet-pink light. After a few seconds this
was switched off and the oil diffusion pump started up.
This pump has no moving parts, but can pull a vacuum of
0.00001mm of mercury pressure, but only if the majority of
the air has been removed by the mechanical 'backing pump'

Next a low voltage, high amperage current is applied to a
heavy tungsten coil - about 50 amps at 3 volts. The coil
becomes white hot and bits of aluminium, or gold, or copper,
etc, which have been clipped on to it begin to boil and
evaporate. Because there is very little atmosphere in the
jar at this stage, the metal atoms get sufficient energy to
travel in straight lines without colliding with air
molecules anywhere in the jar, coating it and anything in
it. Instead of using a tungsten coil, a little boat shaped
dish is sometimes used to contain the material to be
evaporated. Pure silica is often used. You can imagine that
this process is completely controllable, and can give a coat
of any thickness up to a micron or two. Thus an iridescent
effect can be obtained over rocks, cabochons or other
gemstones, including glass.

And there you are; more than you ever wanted to know about
vacuum deposition!


/\ John Burgess
/ /
/ /
/ /__|\
(_______) It's springtime in Mapua Nelson NZ

Subject: NEW: Hood For Star Diamond 10 inch Saw

I am looking for a better hood or a jig to block the mist
from a Star Diamond Industries 10 inch slab/trim saw TS10.
The hood I bought with the unit does not block the mist and
spray that shoots out from the sides. I use mineral oil and
it seems to run with less mist than before but still sprays.

I need to confine it totally. Any ideas?


Robert Redden

Subject: NEW: Need Parts for Vibra-Tek Vibrating Polisher

I have been told that Vibra-Tek is no longer in business.
Does anybody know if the business was taken over by someone
else. I am looking for some tubs and rubber inserts for
the small vibrating polisher.

Bill Louton

Subject: RE: Tumbling Prepolish with Liquid Soap

Craig McGregor said in LD Issue #222, MSG 6 that Liquid
Soap made a fine tumbling prepolish. I wrote to him about
concentration and he replied:

"Just use it as it comes from the bottle: remember it
is the stuff that is used for washing clothes for
automatic washing machines. About the equivalent of
1/4-1/2 cup of dry powder."

I tried the idea and it knocked my socks off! I was going
on vacation for two weeks so filled a tumbler drum (75%)
with "cull stones", poured in liquid soap to nearly cover
and "let it run". The soap was "ALL Laundry Detergent", a
gloppy slimy fluid. Sixteen days later I found that EVERY
stone was polished or semi-polished! The rock raw edges
showed very slight rounding. The fluid had a dense haze
but no sediment.

The cull was from a hodge podge jar of mixed sized scrap
waiting to be sorted and tumbled. I added some pre-forms
and stones from a jar of "won't take a polish" rejects.
Each item now exhibits at least a soft reflection and a few
(agatey) pieces show a high wet polish.

There are pieces of flint where you can see a reflected
light bulb, a little soft but an excellent pre-polish. I
have a piece of basalt with just as good a pre-polish...
(didn't know whether basalt would take a polish). There's
some nice sparkling Aventurine.

So what's happening here? I checked the Lapidary Digest for
previous references and found just a few. Anyone interested
can browse these in the back issues on the LD web page-

LD Issue #70, MSG 7
LD Issue #109, MSG 2
LD Issue #110, MSG 9
LD Issue #110, MSG 7
LD Issue #110, MSG 10
LD Issue #147, MSG 13
LD Issue #152, MSG 10
LD Issue #182, MSG 3
LD Issue #199, MSG 8
LD Issue #200, MSG 14
LD Issue #222, MSG 6

I assume the polishing is due to simple rock to rock
abrasion in the high viscosity environment. To check an
alternate idea, I made up a gum solution which has about
the same physical properties as the detergent. I am now
running a barrel of this against another barrel of the ALL
detergent... same mix of rock in each. I'll let this run
a couple of weeks or so.

For those interested in the techie side, the experimental
gum solution is 12% (wt) medium viscosity, partially
acetylated, Polyvinyl Alcohol with a smidgen of preservative.
I think Gum Acacia (Arabic) would be another bodying agent
which might work. Corn Starch would probably be too "soft".
There are a "ton" of possible agents if rheology is all that
matters, including (maybe) Waterglass.

I get so tired of changing grit, keeping any from washing
down the drain, scrubbing stones before moving to finer
grades and SiC grit isn't that cheap. I see no reason why
this "used" detergent has to be discarded. I'd sure like
to hear from other members who have tried this idea for
good or bad.

Wonders never cease.

...George Butts

Subject: RE: Motor Speed Control

<<I have a GE 1/3 HP motor, salvaged from some piece of
electronic gear or other. I want to run a diamond wheel
directly off the shaft, plus other accessories. But the
motor runs at 3,000 RPM, which is fine for some
applications and a mite speedy for others. Is there a
cheap way of improvising a speed control? >>

Warning. Speed controls can not be used with all ac motors.
It should be noted that motors with speed controls, like a
Foredom or Dremel or old sewing machine motors, are actually
dc motors. The speed is controlled by varying the drive
voltage. The foot pedal actually contains a variable
resistor or what is called a silicon-controlled rectifier
that varies the voltage applied to the motor.

Most larger ac motors (1/3 hp and above) are synchronous
motors. That is, the speed is synchronized with the power
line frequency. The speed of synchronous motors can not
usually be varied since the power-line operates at 60 Hz and
does not vary significantly. (There are some very expensive
controls that will vary the power supply frequency but these
are not usually available for used motors.)

A dc motor that can be used with a speed control can be
recognized by the presence of "brushes". These are evident
as two lumps on opposite sides of the motor. Usually the
"lump" is the head of a threaded cover that can be removed
to replace the brushes.

Using a speed control on a synchronous motor will probably
burn out the speed control and may damage the motor.

Fred R. Sias, Jr., Clemson, SC

Subject: RE: Motor Speed Control

My experience with motor speed control says that you are
basically out of luck.

Most dimmers are made for resistive loads. The problem with
synchronous motor is that they won't handle the voltage drop
too well. It may slow down but your available power will
suffer big time, and likely burn up the beast in time. It is
possible to buy simple dimmers rated for ceiling fans and
they may work for a while, just beware that they are limited
to 300W to 600W duty at full power. Rule of thumb for fans
and pumps is that speed is a function of the power cubed;
that is to say, drop the speed by half and the power
available will drop by a factor of eight. Now the 1500-rpm
motor becomes 1/24 hp.

The only sure way out would be to buy an AC frequency drive.
These guys can vary the frequency from say 30Hz to 180Hz via
integrated electronics (kind like getting the power
company to change the speed of their generators).
I just purchased one last week for a 1/2-hp 120 VAC gear
motor, the price was about $300 and change (the 300 rpm gear
motor unit was $400). This will do the job but only if the
motor is rated for such, i.e., you will need a service
factor of at least 1.5 or more. If the service factor is too
low the motors will overheat thus releasing the blue smoke,
not good. Most recycled OEM motors will be in the 1.0 to
1.15 range.

My advice would be to keep scrounging, or bite the bullet
and purchase a new motor from someone like Grangers or a
discount supply house.

Jeff in Kalamazoo

Subject: RE: Motor Speed Control

The little incandescent lamp dimmers are only good for a
couple of hundred watts and would fry under the back emf
currents developed by motors. Many woodworking and other
handyman catalogs contain similar units that might work
with your motor. These are intended for controlling power
tools and sold as "motor speed controllers". Expect to pay
$40 US or more. Not all types of fractional motors can be
made variable speed.

You will have to watch out for overheating the motor and the
controller. The fan effectiveness is a function of rpm and
the heatload will be high.

Bob Gembolis

Subject: RE: Motor Speed Control

We are so used to solving problems with sophisticated
methods that we frequently forget simpler but well-tested
and reliable other ones.

Have you considered using two multistep v-belt pulleys, with
one mounted directly on the motor shaft and the other on a
separate arbor? These pulleys have three or four steps and
the combination can give three or four different speeds on
the arbor shaft. If you only require a few speeds, you may
be able to find two pulleys which will give these speeds,
or something close to them.


Subject: BIO: James Dumar

Hello from the dry country. I am back online after 3 months
without a phone here at Lightning Ridge. I have enjoyed my
back mailings of lap digest. Very active group, interesting
material always.

My current mining claim is producing.. lots of.. potch. (a
little colour to keep us keen). Me and a couple of mates are
working Indian's Lookout, one of the earliest fields in town

The Coocoran seems to have come back to life in recent weeks,
and there are some claims in Carter's rush for sale that I
have been fortunate to inspect which have cuttable green on
black seam opal in 4 foot runs- both sides of the drive!
Needless to say, those boys are smilin' and askin' a
handsome price.

As to me, James Dumar; I mine, buy, sell, cut, and make
jewellry both in the Ridge, and on my farm near Cairns in
North Queensland. I am an American living overseas since
1974. after living in the UK ,France, and Indonesia
(commercial diver/petroleum). I came to Australia in 1983.
Interested parties check out my web site for information on Lightning
Ridge; I am happy to answer any questions.


James Dumar

Subject: Note: Newsletter from VSmithy

I have just come out with a new price list and newsletter
available via snailmail. If interested, contact me and I
will send a copy to you. It has a review of the book: "The
Opals of the Never Never" by Robert G Haill (which you are
welcome to put in the newsletter) and a copy of my article
on cutting Lambina opals.


Steve Newstrom

Subject: WTB: Gram Scale

Dear Hale,

I am looking for a good used gram scale. I have been
polishing a lot of opal lately and I need to know the
weight of the stones. Does anyone have one they are not

Randy Aue
Estes Park, CO

Subject: FS: Geodes

I have a bunch of Woodbury Geodes, from Middle TN, with
assorted colors and crystalline structures. Some have
cavities and others are solid Agatized Quartz, with
concentric banding in clear, white, yellow, and
orange. Nice slab material.

Subject: FS: Mexican Apache Chrysocolla and Agate

Hi Hale and All,

Thought I'd let you know that I have good supplies of the
following items from Mexico and I am selling them at
wholesale prices:

Apache Chrysocolla - Beautiful chrysocolla color with patches
of red cooperite and silica, green malachite and dark blue
mixed in; solid, does not need to be stabilized; makes
fantastic belt buckles, etc.
$35.00 per lb. with a 2 lb. minimum plus shipping.

Mexican Crazy Lace Agate - Beautiful banded lace agate in
yellows, orange, red and white; some have flower burst
design. $7.00 per lb. with a 5 lb. minimum plus shipping.

Famous Ojo Laguna Agate - Quality nodules of banded agate;
some are banded with different designs and colors inside. $15.00 per lb. with a 3lb. minimum plus shipping.

If interested, please let me know off list and I will send
you the information on these and answer any other questions
that you may have.

Thank you, Hale, for the space.

Thank you,
Duane Pearson

Subject: SHOW: Denver Gem and Mineral Show

Just want to remind everyone of the big Denver Gem and
Mineral Show being held September 17-19 at the Denver
Merchandise Mart at I-25 & 58th avenue.

Subject: SHOW: Fort Osage Knap-in

The Fall Flint Knap-In at Ft. Osage, a reconstructed early
19th century fort overlooking the Missouri River, adjacent
to Sibley, MO, and several miles north of Buckner, MO,
begins its 4-day run on Thursday, Sep. 16.

It is one of the largest knap-ins held in the U.S.A. and it
attracts some of the most skilled arrowhead makers from as
many as 20 states. Pickup loads of obsidian, chert and
flint are common as well as lesser quantities of agate,
jasper and petrified wood.

A Boy Scout Troop prepares most of the necessary meals at
reasonable prices. Twentieth century artifacts such as
painted gourds, bows and stone knives are offered by their
creators. It is a unique event and experience.
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