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stabilizing quartz slabs

Posted by Paul Hewitt  
Paul Hewitt March 30, 2011 01:44PM
I have some beautiful quartz that has pyrite in it. I am trying to polish small slabs and cut some cabs out of the material but unfortunately it has fractures in it. Sometimes it will hold together but more often than not pieces of it go flying when I am working it so my project keeps getting smaller and smaller. Is there something I can do to keep it together not just when working it but after it is cut and polished as well?
Jamey Swisher March 30, 2011 06:06PM
There are many methods you can use for this. It is typically best to do so prior to cutting, but could be done after preforming or pre-polish prior to final polish.

One way is to do the following:
1. Buy the standard size two tubes of Epoxy 330
2. Buy Acetone from Wal-Mart or another hardware store
3. Buy yourself a nice large mason jar
4. Poor a pint of Acetone into the jar
5. Now squeeze both tubes of Epoxy 330 in to the acetone
6. Mix well, stirring is best as shaking can get too much on the seal and the acetone will dissolve it eventually, but the process will be sped up if the liquid itself gets on it
7. Once mixed you can now place your slabs or preforms into the mixture
8. Soak them for 7-10 days minimum.
9. Make sure to agitate the mixture every few days
10. After soaking, remove slabs and place them on a surface that is not cared about, lol. I like the aluminum oven mats from Wal-Mart, like $1.98 or something for two of them, they work excellent for this.
11. Now leave slabs alone for at least another 10 days.
12. They are now ready to cut.
13. But remember if/when selling them or the finished gemstones you MUST disclose that they have been stabilized and you should disclose what method.

Second option:
1. Fill the jar with Opticon (resin) to just cover all the stones by 1/8-1/4 inch over the stones.

2. Place the jar on a coffee machine burner, like an old Mr. Coffee machine. Turn on the machine like you would if you were making coffee and cover the pint jar with a doubled piece of foil (do not put lid and ring on). Cook the stones for 6-8 hrs.

3. After you are done cooking the stones remove them from the heat, take off the foil and pour as much of the Opticon out of the jar as you can, use oven mitts...that jar is mighty hot!!!! After you have gotten the hot resin out, put back on heat for a minute or so.

4. Once you've done this procedure a few times you can empty out the resin pretty fast and don't have to return it to the heat. The whole point is to keep the stones hot.

5. After you empty the resin, place the lid and ring on the jar and tighten. Set aside for 8 hrs. When it cools the lid will pop and create it's own vacuum. I usually start in the morning and then let the jar cool over night.

6. After it has set for 8hrs or more, open up the jar and remove the stones one by one, cleaning off the resin with a paper towel. Use gloves (surgical or latex) when doing this. You do not want to get this stuff on your hands!!!!

7. Get another pint jar out for the hardener, ring and lid also. Place the stones on a piece of foil and take hardener bottle and apply it to the stones (don't use a whole lot but the stones have to be wet). Get a pair of chopsticks or shishka-bob sticks and roll the stones so every part is wet with hardener.

8. Take the jar and run it under as hot of water as your sink puts out, (pre heating it. Don't get the inside wet). When the jar is fairly warm, place the stones (on the foil) down in the jar. I normally shape the foil first to fit down into the jar.

9. Place the jar on the coffee machine burner and cook 2hrs, covering it with foil. About 1 hr into the cooking, get your chopsticks and roll the stones in the hardener at least once. It is very important that you do not breath the fumes; hold your breath when you do this.

10. After about 2 hrs, remove from heat and place lid and tighten ring on jar. Set aside for 6-8 hrs, the lid should pop or suck down on this also.

11. After it has set 6-8 hrs, open up jar and remove stones (with gloves on) and wipe off any remaining hardener. Let stones sit for a day or until they don't feel sticky.

The other method would be to use Water Glass. I do not remember where I got this method and have not tried it yet, but it was highly recommended.

Here's the general procedure that seems to be working now. It's not as involved as it may seem at first glance, and gets easier with practice.

1) Clean slabs (or rough less than 1" thick) in a solution of hot water and trisodium phosphate (available in most paint departments for wall cleaning) prepared in the concentration specified for grease removal. I let them soak overnight. This may cause some slight color change - deeper blues and greens on chrysocolla and turquoise. Rinse slabs thoroughly and allow to air-dry.

2) For this step, you need a shallow, lidded stainless steel (not iron or aluminum) pot or pan and a means of holding temperature at around 180 F, substantially below boiling. I found a thrift store electric buffet warming plate which worked nicely. The stabilizing formula is based on sodium silicate solution with a weight ratio of around 3.2 (available at and other similar sources). Read the MSDS! This solution is caustic, and you should wear eye and skin protection to handle it. Spray the pot lid edge with PAM or other cooking spray to keep it from adhering to the pot. Clean up drips and used utensils immediately with warm water. If the solution gets on fabric, rinse and wash it before the silicate dries.

3) Now, this is where things get a little weird... it takes a combination of very low activity organic acid and alkali mineral salts (carbonates, phosphates and sulfates of calcium, potassium, etc.) to get the silicate to polymerize in a non-water-soluble form, e.g. as agate. Though this can be done with very concentrated mineral water (about 1 gallon boiled down to 1 cup) and aspirin or citric acid, I found the easiest and cheapest way to do this was with Emer-Gen-C Lite mineral supplement packets. ***It's important to get the Lite sugar-free version --- sugar or fructose will oxidize and may discolor the stones.*** Dissolve one packet of Emer-gen-C in 1 cup (approx. 250 ml) of water and allow the fizzing to disperse. Add this solution to 8 oz. of sodium silicate in the stainless steel pot and stir to mix. For stones with very fine porosities or hairline cracks, add about 1 teaspoon of liquid dish soap to reduce the viscosity of the solution.

4) Submerge the slabs in silicate solution in a single layer. Stacked slabs may stick together. Cover and let stand on the heat source for at least 24 hours. Longer cooking won't hurt... I've left some material in for up to 4 days. Remove the slabs and set them on a spray-greased baking rack over newspaper. Allow the slabs to drip dry. The dried slabs are safe to handle bare-handed, and can be gently pried off the rack if they stick. A word of caution --- dried silicate can be as sharp as glass!

5) Place the dry slabs on a cookie sheet and set in a cold oven. Turn the oven to "warm" and leave it on overnight. Turn the oven off and allow the stones to cool to room temperature with the door closed. The slabs should look shiny and any deep cracks will be partially filled. Porous stones should feel noticeably heavier after this treatment. At this point, you can re-clean the stone and "paint" silicate formula to fill larger cracks and voids. Repeat the drying and baking processes to set the added silicate.

The whole cleaning, soaking, drying and baking process can be repeated as many times as you feel necessary. There may be some brownish surface discoloration on the stone, but this comes off with polishing.

Silicate solution can be reused multiple times, adding a little water to replenish the volume. The solution may have some precipitated white silica gel and will turn tea-colored. When a thick layer of silica gel has precipitated and the solution seems thin, treat it by pouring out on about a pound of scoopable cat litter, allowing the litter to dry, then discarding it in regular trash. Don't pour it down the sink.

I've tried to explain in as much detail as I've gleaned from a half dozen or so different trials. So far, it's worked on slabs and rough of many different jaspers, chrysocolla, turquoise, Laguna, Botswana, plume and moss agates, Koroit opal, petrified woods and fossil coral.

Hope this helps.

Registered Gemologist
Research Gemologist
Club President/Owner
Rock Currier March 30, 2011 07:42PM
Article, Article, please, please!

Rock Currier
Crystals not pistols.
Paul Hewitt March 30, 2011 09:08PM
Great info Jamey! I read about those methods in a different thread but they were for a different mineral (serpentine I think) and I wasn't sure if they would work for me. I can't wait to try it!

Jamey Swisher April 03, 2011 06:15AM
Already done Rock!! hehe. ;)

Yep, these methods will work for almost any materials. The Epoxy 330 & Acetone method works best for very porous materials. Sometimes some follow up surface filling might be needed if surface is very pitted.

Opticon I typically reserve for opals and such.

Only tried the water glass once, but not the method referenced above, on turquoise, worked nicely. I want to try the method I listed above though, see if it really does what it is touted to do!

I've been experimenting a lot with treatments on various materials from agates and jaspers to colored gemstones. Trying to figure out how the overseas sellers are managing to clarity enhance everything from garnets to quartz/amethyst/citrine to spinel to just about everything. I have figured it out as well, just have to finish testing and write the research paper up on it. ;).

Just got done playing with heating zircons via stove top, we have an electric stove with the tempered ceramic glass over the entire top and burners. Worked out excellent as well, except for one dark red one that turned black and abruptly exploded, actually it was the table and part of the girdle just blew right off the cut stone, lmao! Got Imperial colored ones to turn a beautiful yellow, dark red to turn into that gorgeous pinkish red that is so sought after, got one dark red to lighten a bit, got a green one to get back its sparkle, got some nasty dark orangish brown ones to turn into candlelight zircons and some light pinkish ones, and some dark browns to turn into nice honey and cognac colored ones. All and all a fun and productive time.

Sorry for rambling. Just researching treatments right now, so it is an exciting topic for me, if sellers would just remember they have to disclose that the material is treated and how it is treated, lol.

Registered Gemologist
Research Gemologist
Club President/Owner
Rock Currier April 03, 2011 08:03AM
Ive heard that the guys in Thailand are the the zircon heating masters but much of what they know/knew is going away because they don't use zircons much any more as diamond stimulants. I wonder if you couldn't find some of the old guys there that would tell you a lot if you just asked them?

Rock Currier
Crystals not pistols.
Jamey Swisher April 07, 2011 06:24AM
No clue. I kind of like just experimenting though, that is the whole fun of it, hehe. ;). It is a puzzle to me that I just like to figure out if I can. So far so good. :)

Registered Gemologist
Research Gemologist
Club President/Owner
Rupert Harrison April 12, 2011 06:53PM
Hi Jamey

I've got a large slab of Mendip Agate from Somerst, England, which was cut from a large geode I found in a pile of discarded topsoil in an old quarry.

I'd like to polish it later this year, when I will have my newly purchased lap polisher set-up. My concerns are that the slab has several visible open cracks radiating out from crystal pockets in the centre to the outer edge. I'd like to stabilize the slab by filling-in these cracks, but I dont want to affect the lusture of the crystals in these pockets. I'm wondering if the immersion processes you describe will be suitable. The diamond saw used for slabbing it was oil-cooled, so the slab has absorbed a certain amount of oil as well.

Please can you advise.


Jamey Swisher April 26, 2011 06:36AM
Thee method may work to stabilize it, but it will not fill the gaps, you would need.Opticon our even just Epoxy 330 without the acetone to fill the gap, add some crushed rock in the epoxy or resin for a more natural filling process.

Registered Gemologist
Research Gemologist
Club President/Owner
Tim Jokela Jr May 21, 2011 02:21AM
Opticon works great, but you have to follow the instructions and beware of humidity and shelf life.

Fact is, in my experience, that it's generally not worth the bother to stabilize cabbing material.

Chuck the fractured stuff out behind the house and spend your time on quality material.

Much time and $$$ saved.


Jamey Swisher May 21, 2011 05:51AM
It all depends Tim, there are lots of materials that need either backed or stabilized that bring big bucks cabbed! Turquoise comes to mind, the real stuff that is, lol.

Registered Gemologist
Research Gemologist
Club President/Owner
Eva Jarne October 24, 2011 11:25AM
I am an amateur rock cutter in northern Europe. After spending several days carving aventurine an ugly fracture opened. I don't want to throw the material and work away, so I tried treating it with the instructions above on this page:

- mixed the 2 parts of clear epoxy (10 minute epoxy by Loctite or Casco, don't remember which) into 1/3 litre acetone. Seemed to have dissolved well, the solution was thin and clear. Closed the lid and let it stand at room temperature (approximately 20 celsius)
- stirred twice during the first day, and once on the second day
- on the third day a white gel was floating around in the acetone and on top of the stone; evidently the epoxy had separated from the acetone, and was starting to form a thick cover of messy glue on the stone.

Getting rid of the white gel and cleaning the surface of the carving was quite a messy business. The acetone melt my disposable gloves in a blink, the sticky gel was all over my hands, couldn't pour it down the drain, etc., etc..

What went wrong? Too much epoxy and too little acetone? Wrong type of epoxy?

Thankful for any help,
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