Cutting stone and rock

Hello All

I have a question to the lapidary people/Pros who do cutting slabs
and rough rock. a few years back i had purchased quite a bit of
rough rock of variuos types that are of intrest to me, trying to
carve and cut my is highly time consuming to say the least,
and also an added expense with the equipment… well my question is,
i have rough dendiriatic sage amethyst agate,that has a lot of clay
like softer spots, unusable, so when you come to a batch like this
that has none usable parts, what is the best, fastest, least hand
labor involved technique to go with? I know it needs to be removed.
and was soaking it in water to soften and pick and grind. all hand
done. I know some use tumbling, these are larger pieces of 3x4x3
inches. anyone know of a different way’trick?

i also have a bit of blue Opal from oregon that has similar unusable
parts, do i use the same techniques on the opal? i am not sure about
this bit of info but I had read and heard talk of opals not doing so
well with introduction to moister and water?also noticed some of this
opal sitting on a window sill getting paler incolor? is that the same
in the australian lemon chrysoprasse? UV sensitive?I will stop here
not to add confusion to the questionsthanksin advance for your time
and attention

Hratch Babikian

I went into “sticker shock” when I looked at the price tags of
commercial slabbing machines. I needed a saw for my prospecting work
which would give me test cuts into rock samples but did not require
the great precision of a slabbing machine. Google on “King Saws”
(Ontario). For less than $200 I bought a King chop saw with 14 inch
blade. Caveat emptor when it comes to safely handling this with rocks
as it is designed only to cut steel rods and such. But it worked well
enough with a diamond blade at about $100. Lots of dust was created
because the blade is rated for dry use so I use it outdoors and dust
mask is also wise.

What I would like to do now is send some of the blocks I have chopped
up to somebody with a stone lathe who can cut/carve some simple
shapes into them. Does anyone on Orchid have a stone lathe?

I have used my ultrasonic cleaner to get at most of the loose
material, but only on the harder rough material. I do not recommend
it on opal or other like materials.

Another cleaning item can be one of the water cleaners of teeth like
the Water Pik.

Good luck,
Ken Moore

Hratch; Opal has some water loosely attached in its chemical make
up. Some opal has a tendency to crack when it dries out. Especially
Virgin Valley opal. Some people keep opal in water to avoid cracking
and to enjoy the colors and fire. But if the opal is going to be
worked it is better to hold it dry for a year to see which will crack
and which will stay whole. That way you do not waste a lot of time
working a stone and then have th finished piece crack up.

It is reccomended that opal jewelry be taken out and worn
occasionally to help keep it hydrated. The moisture in human skin is
good for them. Avoid heat with any opal. Hot sunshine on a windowsill
can cause an opal to crack up. Yes, they can also lose color. I knew
a dealer who ruined a bunch of fire opal by leaving the batch in a
box on top of a steam radiator. They looked like those heat treated
crackled marbles that were popular a few years ago.

Never hot dop an opal either. Work it with plenty of water and avoid
working it to the point you get it hot. Some folks will finish off
stones with a dry finish polish. This works fine on jade, but not on

Rose Alene

I use a Mystic Spot Spray gun. It will blast all the soft stuff


Most mineral dealers use one of those hand held high pressure fabric
guns that shoot out a fine water jet. “Red Arrow” is a common brand,
the price of these is or was in the 100+ dollar range. These guns are
powerful; they will blast water through your skin; soft stone can be
carved with them. But for getting dirt out of crevices they are
wonderful. I have not used a water pik toothbrush but have heard it
recommended for more gentle action.

Now to correct an opal misperception, most Australian opal can be
hot dopped with no problem whatever; I do so routinely and as I
recall that’s how it’s done in Lightning Ridge. Mexican is more
dicey. Some are indeed heat sensitive, in my own experience
particularly the crystal and fire opals without matrix although I’ve
seen lots of Mexican white base craze also. The often cited practice
is to torture test Mexican opal by leaving it on a hot tin roof for
six months to a year, out in the sun, something like that. Rough
which has not crazed after this time is assumed to be stable and
suited for cutting (in a no-guarantees, this is the best we can do
sort of way). So the dealer who put his Mexican material on a hot
radiator and “ruined” it can be assumed to have acted from this
purpose and not from ignorance.

Hans Durstling
Moncton, Canada

If you are trimming off a slab, a trim saw will speed you along, if
there is a lot to remove you can notch the slab and snap off pieces
with long handled pliers. If you have chunks and you can tumble them
that will help too, I will throw stuff like you describe into a
tumbler with medium grit for a day or so, not enough to grind much
off but it will remove soft stuff. I also clean things up with an 8
inch silicon carbide wheel and water drip. If you have pretty rock
that you would like to cut but it is too thin you can back it with
some steel filled epoxy. I do that with boulder opal, it is too
expensive to waste!

Ben Brauchler

For removing waste rock I start with a heavy wooden mallet, if
further material needs removing use an old screwdriver like an
ice-pick (hammer optional).

On opal I wouldn’t worry about it, just slab it up and the waste
rock will crumble away or can be trimmed away.

Happy slabbing!