Hello, Thank you everybody who answered my questions about what lapidary
machines to start off with. I decided on trying the All You Need by High
Tech. I received it last Thursday and I can’t get off of it! I can finally
start cutting all that rough I keep buying on e-Bay! I have question
though: Is anyone familiar with Peruvian Opal? I purchased a kilo of blue
dendric and a kilo of pink (very different material from each other), and
have been cutting it all week. I love the pictures in the blue but find
that polishing with the 14,000 diamond compound produces fractures on the
clean pieces, even at low speeds, anyone have any ideas? Also, I’m about to
set a bunch into jewelry for an upcoming show, does anyone know the value
of this stone cut? I’ve never seen it before, so I don’t know the
market…or is it up to me to create one!
Your problem with the blue Peruvian opal is that you’re getting it way too
warm when you polish it; either too much pressure, speed, or both. I’ve had
perfectly transparent stones go opaque at that stage for the same reason. I
finish mine on cerium oxide, on hard felt, very wet now.
Dear Amy, I have some experience with the Peruvian blue opal. You might
have better luck polishing with cerium oxide. I’m not sure if Hi Tech
sells it but you can get it from any lapidary company. You can use it on
the Tech 10 pad (I think you’re using that for the diamond compound) with
enough water so the stone doesn’t get too hot. Alot of the blue opal I’ve
seen tends to craze or crack in dryer climates. I hope what you have is a
good batch.
To Amy re the Peruvian Opal question: Donald K Olson in Bonsalls,
California, has had some of the pink cabbed at the San Mateo Int’l Gem and
Mineral Show - his # is (760) 758 - 2388. He and his wife are both
extremely knowledgeable and, my experience is, very helpful with
He will certainly be able to direct you to others if he can’t
answer your question. There is another person who shows and sells the blue
Peruvian Opal at San Mateo - he’s from Northern Oregon but I can’t find
anything with his name on it. IF you don’t need to know before the next
show (Sept. 11-13), contact me off-line and I will tell you how to find him
at the show.
I also have two pieces of the pink cabbed (from Olson) and can weigh it and
calculate what they charged per gm finished. Let me know if you would like
me to do that. Hope this helps
I’ve never cut peruvian opal but if it is like precious opal it does not
deal well with heat. Diamond can heat up a stone fast, and that might be
part of the problem. You might try using tin or cerium oxide on a felt or
leather buff instead. ur later and the cussed thing was riddled with
cracks.
HI: It would seem that you are getting the stone hot internalt, as the
hardness is not that much you should not have to use 14,000 you can buff
with chrome oxide on a medium buff wheel or a soft leather, I have used
that motheod for years and as long as I don’t get the stone to hot in one
place every thing comes out good… Hope I have been some help. Oh and
water cooled wheels are the best way to cut opal at least in my
experiance. I have found the all u need to heat up stone very fast…
Perhaps they have a pad with more nap to it.
Cerium Oxide or Linde A on damp (or almost wet) leather will bring up a
nice polish on opal without heating the contact point too much (probably
why it is fracturing).
I have (I believe) some of the opal you are referring to. Light to medium
blue with a lot of black dendrite-looking inclusions and some white wispy
inclusions, too. Let me begin by saying this stuff is unlike any other
opal I have ever worked (I’ve worked a lot of opal). I have managed to get
a reasonable polish on it using 14k, followed by 100k grit diamond. You
may be overheating the stone, causing the cracks. Any time I polish opal
with diamond, I use short bursts of time on the polishing lap. In between
these bursts, I check the temperature by touching it with my finger. I
also add a few drops of diamond extender fluid or mineral oil to the lap (I
use the Hi-tech polishing pads). I have never been able to get a really
good polish on that opal. I’m still trying new things. Cerium seems to
get about the same results for me as diamond. Since I’m a stickler for a
good polish, I wouldn’t sell any of my finished pieces. I haven’t seen a
good polish on anyone else’s finished pieces either, so I don’t feel too
bad. That particular opal has an extra waxy lustre that I’ve never seen
on any opal before. I’m real tempted to say that it’s not truly opal, but
I’m no gemmologist so I can’t be sure. It is very beautiful and
interesting stuff, though (I for one, love inclusions). If I find any great
new way to polish it, I’ll let you know - Hope you’ll do the same!
Mark & Pete, Diamond extender fluid is silicon oil and may be found at
machinist supply companies. I have found it at local industrial surplus
dealers in three cities. MArcus
Re: using extender fluid and mineral oil interchangeably… Hmmm… I
can’t say for certain, as I have several diamond polishing laps and have
used one or the other or both fluids on all of them… Kinda grab whatever
is closest at the time. I’m pretty sure I have used both. Two of my laps
are over ten years old and are just “well broken in”. I’m pretty sure
there’s a little of both on each of them. I will say that it lasts a long
time. I just used one of these laps last night that hadn’t been used for
many weeks. I didn’t even need to recharge with a “squirt” of polish…
It was still oiled slightly and polished up some natural turquoise and
sugilite quite nicely. As a matter of fact, I have always wondered what
that extender fluid actually is. It acts just like mineral oil…
Marcus and Mark, If the extender fluid is silicone oil, then it should mix
with mineral oil without any problem. I’m guessing that both silicone oil
and mineral oil are an awful lot cheaper than “diamond extender fluid”.
Cool! -Pete-