Unakite for Rock Tumbling and Cabbing
This image shows a 3-pound bag of unakite rough, dumped into a colander and sprayed with water to reveal its full color. Click on the image for a larger view. This rough shapes quickly in a tumbler and produces beautiful green and pink tumbled stones.
Unakite Tumbling and Cabbing Rough
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Size: mostly 3/4" to 1 3/4" pieces
Unakite is an interesting igneous rock composed mainly of pink and green mineral grains. There are very few rocks made up almost entirely of orangy-pink and yellowish-green minerals, so, once you are familiar with unakite you should easily be able to identify it when you see it again.
Unakite is named after the Unaka mountains in western North Carolina and eastern Tennessee. It has been quarried there for ornamental and construction stone since the mid-1900s. It has been used to make flooring tiles, facing stone, curbing stone, paving stone, stair treads, countertops, window sills, lentils, ashlars and many other products.
Unakite is also found in many other parts of the world. Today, much of the unakite used in dimension stone and lapidary projects is quarried in South Africa, Sierra Leone, China, Brazil and Zimbabwe. The unakite being sold here is from South Africa.
What Is Unakite?
The orangy-pink mineral in unakite is orthoclase, a mineral of the feldspar group. Orthoclase is the mineral with a hardness of 6 used in the Mohs Hardness Scale. The yellowish-green mineral is epidote, a rare mineral found in a small number of igneous rocks and low-grade metamorphic rocks.
Unakite is an igneous rock that is very similar to granite. Much unakite forms when granite is altered by hydrothermal metamorphism. The main difference between granite and unakite is the presence of significant amounts of epidote.
Unakite as a Lapidary and Jewelry Stone
Unakite is slabbed and cut into cabochons for jewelry use. It is also cut into beads, and tumbled into polished stones. Unakite is used to make spheres, desk sets, vases, small sculptures and many other objects. It is a popular carving and bead-making material because it works easily, and, its hardness of 6, allows it to shape more quickly than quartz, agate, jasper and other common materials.
INTERMEDIATE Rock Tumbling Recipe:
Unakite (3/4 to 1 3/4 inches)
Unakite requires special attention during rock tumbling for two reasons:
1) Shapes Quickly: Most of the minerals in unakite have a hardness of 6. So, they will require less tumbling time than jasper and agate to achieve a nice shape. If you tumble too long you will lose weight.
2) Media Needed: Both orthoclase and epidote have perfect cleavage - and they cleave easily. So, they must be tumbled gently to prevent breakage and bruising. We recommend using at least 25% media during the medium grit, fine grit, and polishing steps.
Recipe for Rotary Tumbling
Barrel slurry dumped down the drain will harden like concrete.
Coarse Grit Step: Fill your barrel 2/3 full of rough and media (or small rough). About 10% to 20% of the material in the barrel should be ceramic media or small size rough. Then add 2 tablespoons of coarse (60/90) grit per pound of material in the barrel (rough + media). Add enough water to cover the rocks and tumble for one week.
Medium Grit Step: Put your cleaned rough and media back into the barrel. If the barrel is less than 2/3 full, add additional broken-in media to get the barrel up to its proper operating level. Then add 2 tablespoons of medium (150/220) grit per pound of material in the barrel. Finally, add enough water to put the water level just below the top of the rocks. Then tumble for 1 week.
Fine Grit Step: After clean-up, put the rocks and media back into the barrel with 2 tablespoons of fine grit per pound of material and enough water to bring the water level up to just a little below the top of the rocks. Tumble for one week. Your rocks should be really smooth after this step.
Polish Step: Make sure that your barrel and rough/media mix have been cleaned thoroughly of all grit and rock mud. Then place the rough and media in the barrel with two tablespoons of TXP polish for each pound of material in the barrel. Then add enough water to almost cover the rocks. Tumble for one week.
Burnish If Needed: If you have done a good job of tumbling, this tumbled unakite will have a nice soft glow. It will not have the "glassy" polished luster that you can produce on agate. Burnishing will probably not be needed, but if you want to clean up the rocks, you can find the full burnishing instructions here.
Vibratory Tumbler Recipe:
1" to 3" softer rough
Coarse Grit (60/90 Mesh):
Coarse grit is not used in a vibrating rock tumbler.
Medium Grit (150/220 Mesh):
Due to the size of this material it is recommended that you start with minimum of 30% ceramic media. The use of this media will aid in the tumbling action in the barrel and help deliver grit to all surfaces of the rough
After you have your bowl loaded to the manufacturer's recommended level add 1 tablespoon of grit for every two pounds of material, including the media, in the bowl. While the tumbler is running, slowly add water until the material has a thin coat of wet grit and the tumbling action is smooth and fast in the bowl.
Check the bowl every 8-12 hours to ensure the action is still good. If the action has slowed, add water a little at a time until the action is back to normal. If the mud gets too thick you will need to do a complete rinse of the material and bowl. After rinsing, add fresh grit and water and start tumbling again. You are done with medium grit when you are satisfied with the shape and smoothness of the stones. Usually 3-4 days for us with this material. Give the material and bowl a thorough cleaning before moving on to fine grit.
Fine Grit (500F Mesh):
Place your material back in the tumbler bowl, then add enough polished ceramic media to bring the load up to the manufacturer's recommended operating level. Add one tablespoon of grit for every two pounds of material in the bowl. Then, turn the tumbler on and slowly add water until the material has a thin coat of wet grit and the tumbling action is smooth and fast in the bowl.
Open the bowl every 8-12 hours to check the action is still good. We usually run fine grit for 48 hours. Thoroughly clean the bowl and material before moving to the polishing step.
Polish (#61 Rapid Polish or TXP):
Place the cleaned material back in the bowl. If needed, add ceramic media that has been previously polished, to bring the bowl up to the manufacturer's recommended operating level. Add one tablespoon of polish for every two pounds of material in the bowl. Turn on the tumbler and slowly add water. Stop adding water when the material has a thin coat of wet polish and the tumbling action is smooth and rapid.
Like the previous grit steps, open the bowl every 8-12 hours to check the tumbling action. Add water if it has slowed. We have found that 48 hours is usually all the time you need to get a good polish in a vibratory tumbler. Any more time than that and you run the risk of damaging / bruising the material.
Burnish If Needed:
This rough will usually take a great polish. However, burnishing this material after the polish step can often improve the look of the finished stones. If you would like to try burnishing to see if it improves the look of your polished stones, full burnishing instructions can be found here.
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