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Polishing Lapis


#1

Hello all, Okay, this is the most basic of basic lapidary
question. I have a medium sized Lapis cab someone needs me to
polish and set. What type of wheel and what type of compound do I
use. Can I do this at my regular polishing lathe? I use the basic
green and red rouge, felt and muslin buffs for jewelry, so that’s
what I’ve got. I have never done any stone cutting (although I AM
taking a lapidary class later this summer to alleviate my
ignorance!).

Thanks,

Amy O’Connell
Amy O’Connell Jewelry
http://www.ezmo.com/amy


#2

Lapis can polish 1 of 2 ways, depending on the pieces grain
size:

  1. fine grained. Grind / sand as usual, through 3,000 diamond
    (carbide will also work). Polish WET with cerium on leather,
    vinegar added to mix.

  2. medium to coarse grained. For polish, use 50,000, then
    100,000 diamond in place of cerium above.

Hope that helps.

Mark Zirinsky, Denver, CO


#3

Amy: What you need is a basic lapidary cabbing machine. You can
get the serious model for about $1100. to $1500. or the simpler
(and much cheaper) model I have. It’s called the “all-you-need"
made by Hi-Tech Industries. Available from A&B Jewels & Tools.
1-800-62-tools. It sells for about $350.00 complete with all the
supplies. It’s a horazontal 6” rotating disk machine. Very
compact and complete.

Best;
Steve Klepinger


#4

Hi Amy,

You can indeed use your polishing jewelry lathe for this. Since
you already have the cab I would guess it just has a crappy
polish and does not need any prepolishing steps. Attach a hard
felt buff (I like 3") and charge with either Zam or Fabuluster.
Either of these will quickly bring a very nice polish to Lapis.
If you don’t use either of these compounds and don’t want to buy
them just for this project then first try whatever type of rouge
you have laying around. Although I have never tried it with
rouge, I suspect that it might work alright with a little extra
polishing time.

@DMorton567


#5

Hello, Having been a repair jeweler for many years and a
lapidarist, I have found several methods to polish lapis. because
of the combinations of material the stone will undercut easily,
so I always take a piece of 600 grit diamond cloth (sandpaper)
and use that to smooth the surface and take out the wear then i
use a small flex shaft wheel (if the stone is in place) and emery
buff lightly, I then go to a finish polish and buff well, if the
stone is out much better, use a small nail up to 16 penny and
coat the head with doping wax. Attach the stone and buff. I then
finish with a silicone wheel to a brite polish. RINGMAN John
Henry


#6

Amy I wouldn’t get rouge of any colour near that Lapis
personally. Lapis is a soft stone in lpaidary terms - about 5.5
Mohs and a s such can be a bit of a swine to geta good polish on.
I like to sand down with diamond to 3 micron on hard pads the
polish with chromeozide on leather. I find I get a better polish
this way than going all the way with diamond. I would suggest a
tame local lapidary if you have one - it won’t take long, I
regularly repolish stones while the customer waits and watches -
aids the concentration somewhat I must admit! Andy

Andy Parker, Agate House Lapidary
Ulverston, Cumbria, England
http://www.netcomuk.co.uk/~andyp


#7

Hello Amy, STOP! don’t be using any of those thngs on lapis, you
will make matters worse I guarantee. Lapis is one of those
problem stones that can frustrate an experienced lapidary who is
not prepared to accept the typical orange peel finish. A high,
almost agate like polish can be achieved with succesively finer
grit diamond paste on a series of wooden, corian, or rubber
backed canvas laps. If you don’t have access to this equipment I
wouldn’t recommend doing anything yourself. I think it’s time to
join your local rockhound/lapidary club and start to enjoy stone
cutting the easy fun way, with proper lapidary equipment.

Tony.
\ () || | /
\ /
\ /
@Anthony_Lloyd-Rees
http://www.opalsinthebag.com
ICQ# 15173706


#8

Amy, Take a strip of thin, soft leather…I use buckskin…then
make a thin paste with water and cerium oxide or aluminum
oxide…available from lapidary supply houses such as Alpha
supply or your local rock shop, hobby shop or whatever. Dampen
the leather, then apply a little paste and buff the stone. You
can lay the leather on a soft pad and rub the stone against it or
hold the piece an a vise, assuming the stone is mounted in a ring
or some such, and buff it as you would a shoe. If the stone is
really dulled, you may have to sand it with a piece of 400 or
600 grit wet or dry paper before polishing. You can do this
fairly quickly with such soft stones as lapis, turquoise and
opal. Even agate can be done this way, but it takes a lot longer.

Jerry in Kodiak


#9

Hi Amy,

I am assuming from your post that the cab is already polished
somewhat and just needs to be cleaned up. If so, depending on
how deep the scratches are you may have to start with a fairly
course grind. If they are just minor blemishes - not scratches -
you can try Zam. However, usually the buffing compounds for
metal are too coarse to leave a high polish on stone. I use
diamond on a flat lap and usually finish lapis with 50,000 or
100,000 grit for a high polish. You will love lapidary, but be
careful it is easy to ‘get hooked’ and buy all kinds of stone
because the design opportunities just explode when you can do
your own. I have more stone than I will ever, ever get around to
cutting and have discovered it is better (more profitable) for me
to find a full time stone cutter who will cut to my specs.

Nancy Bernardine-Widmer
Bernardine Art Jewelry
http://www.bernardine.com


#10

Lapis is realtively soft - about 4 on the Mohs scale. How much
polishing depends on how deep the scratches are-of course.
Someone who regularly cuts and polishes cabs, could probably make
a good guess at what grade of abrasiveness to begin a repolish
job. The more coarse abrasive moves more material faster than a
finer abrasive. Basically, the principle is to use only the level
of abrasiveness that will remove the deepest scratches. The to
work “forward” to finer abrasives to remove the scratches left by
the previous abrasive, until you get to the polish stage.
Depending on the stone, a common final polishing powder is
cerium oxide.

But since you’re new, you might try this method.

For a stone like lapis, you go “backwards” in abrasivesness.
That is, use the polishing rouge (or better yet zam) and see what
that does. I doubt that you will get the high shine that cerium
oxide provides however. If you’re happy with the results, great.
If not go back a step to tripoli; clean, and move back to zam.
Zam is a little kinder than other polishes to soft stones such as
lapis and turquoise.

If the tripoli doesn’t remove the scratches, don’t go down to
bobbing compound, as that may remove way too much material before
you realize it. Then you’re hosed! Find someone who has lapidary
equipment to do the job for you.

BTW: Lapis is beautiful material, but not a good choice for a
ring worn everyday. You can’t wear lapis rings when ya scrub the
sink! You may want to invest in some cerium oxide powder to put
on a small hard felt wheel in you flex shaft for just this type
of job. Wet the pad and the stone, then apply the cerium oxide to
the pad. Ya don’t need much. A little dab-2 cubic mm is enough
for a small stones.

Cheers

Virginia Lyons


#11

G’day; As lapis is a fairly soft, slightly porous stone it is
very difficult indeed to get the kind of mirror polish possible
with agate or jade, but it is not difficult to get a very
reasonable polish. I use a flat lap rotating at about 800rpm
with a water drip (any faster and you’ll get drowned) using 180
grit, then 300 wet, followed by 400 wet-and-dry paper, but turn
off the water for the 400 grit. you can see a beginning polish
with the 400 but tin oxide on a hard backed leather lap gives an
excellent polish quickly. At a pinch, it is possible to get a
reasonable polish on lapis entirely by hand - the ancients did
it all the time. I find that the polishing mops used for metal
finishing are not good for stones. The whole job takes only a few
minutes with the right gear - and there lies the rub! I’d offer
to do it for you - if we weren’t on opposite sides of the world.
Cheers,

        /\      John Burgess
       / /
      / /      Johnb@ts.co.nz    
     / /__|\
    (_______) The basic premise of The Scientific Principle is 
  that everything in the entire Universe is capable of logical 
  explanation by humans.

#12

Speaking of polishing scratched stones. I wear a garnet cab
pinkie ring all the time. The garnet has become scratched and
has a slightly dull, matte finish. I know nothing about
lapidary. Can I polish this in my home studio or should I take
it to a “pro”? Gini in St. Petersburg


#13

Hi, Lapis, depending on the quality, is usually somewhat
porous, and I would not polish it with anything that might get
into the pores and be next to impossible to remove. Just a
thought. Diamond pastes are cheap, can be used with a 1" buff,
and leave little residue.

John g


#14

Hi Amy! Anthony is right - Lapis is a problem stone, because it
contains several different minerals of widely varying hardness.
I have diamond tools, and I would be happy to repolish your
stone, and explain to you how it was done - so that in the
future you can purchase the tools you need to do the job
yourself. Please let me know what you’d like to do. :slight_smile:
Salutations from the summery Cradle of Winter, Pete Buffalo, New
York


#15

Sorry I had forgotten to say what I use for polish. I use cerium
oxide with a 50/50 mix of vinegar and water on a muslin buff to
get my finish polish. This also works well on jade, only use a
leather buff. I use the wheel to get the edges clean and the
under cut smooth. If I am In my home shop I use a genie 8" wheel
lapidary unit, Nice to have but does not travel. Hope I got
things a little more clear. I also have an all you need but find
that cabs are better cut on a round wheel.

Thanks for the Orchid group It has been a wealth of
Ringman John Henry


#16
       Lapis is a soft stone in lapidary terms - about 5.5
Mohs and a s such can be a bit of a swine to geta good polish
on. 

Just curious, but I was given some lovely rough Lapis from an
Afghani Lapis dealer some years ago, he told me to be sure and
polish it with tin oxide. Would that be a good idea? I just came
across it again, when this lapis thread came up, and I thought
I’d ask.

Lisa, (spent the day at IKEA,(enourmous cheap Swedish home
furnishing store),…and now I feel Like a rat having just
survived the maze…cheese anyone??), Topanga, CA USA


#17

Amy,

I agree with Tony. I have polished lapis(My very favorite
stone) for years first with hand or machine sanding then move to
a canvas on a very thin rubber pad backed by hard wood, it is
about six inches in diameter and I use 3000 grit diamond powder
and a spray of misted water then move to 8000 grit…then move to
a cloth(thick almost like velvetine) on the same hard wood disc
with no rubber cushioning. I can achive a glossy finish with
just a little work.

Quickly wash to clean never let sit long in cleaning solution or
the gloss will be removed. This is not as hard as it might seem
but if there is a local rock club they will be glad to give you
help I’m sure. Ron Kreml


#18

Garnet is 7-7.5 on the mohs hardness scale…considerably
harder than Lapis (5-5.5)…and somewhat harder than agate (7).
You need pro tools…or a pro. I’ll gladly do it for you, if
you’re not in too much of a hurry (travel time
South-North-South.)

-Pete-
-Buffalo, New York-


#19

Ginny it just needs refinishing… Any lap person can do it in a
few minutes for you… If you lived down the block I would do it
for you…I used to do my pinkie ring all the time… course I’d
do it for nothing if you let me take Alan’s class.,.,.,…
calgang. Ps I’d still do it for nothing…if you lived down
the block…


#20

Garnets are very hard – 9 on the Mohs scale. Try just washing
it in mild soapy water and see if that does the trick.

If not, I doubt that you have the correct tools, and if it’s a
faceted stone, you’ll don’t want to ruin the facets. Take it toa
pro.

BTW: Garnets are pretty inexpensive. You might consider
replacing it.

Cheers

Virginia