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There are more than twenty different species of garnets but only five species of garnets worth cutting and polishing. They are grossularite, spessartine, almandite, pyrope and andradite. The main reasons why they are great for cutting and polishing is they all have the same crystalline structure, but their chemical composition is different.
You can cut and shape garnets with wet-dry sandpaper and some water or the engraving attachment on a Dremel. Only tumbling grade garnets should be polished in a rock tumbler. For a final polish by hand, use some aluminum oxide polishing compound on a piece of denim or the Dremel’s polishing wheel.
Before cutting and polishing a garnet, you need to remove any remaining rock matrix and dirt. Inspect the garnet with a jeweler’s loupe or magnifying glass for fractures and inclusions and decide on the best shape for it.
If you are interested in checking out the best books about rocks and minerals identification you can find them by clicking here (Amazon link).
Is Garnet Hard To Cut?
Garnets range in hardness between 6.5 and 7.5 on the Mohs hardness scale, so they are hard enough for jewelry. Pyrope, spessartine, almandine and tsavorite are harder than most. They are not hard to cut, and many gem cutters love them, saying they can be cut into just about any shape.
To bring out the best in a garnet, it must be faceted after being shaped. How you do this depends on the shape and size of the garnet.
Cutting facets into gemstones is a skill and an art that requires a faceting machine for best results. You can try faceting garnets at home using some basic items, but valuable stones should be taken to a gem cutter.
Cleaning Garnets With Vinegar (Before Cutting & Polishing)
The safest method of cleaning a garnet is with dish soap, water, and a soft cloth. Don’t use a steam cleaner. You can also put garnets without cracks in an ultrasonic cleaner.
If there is still some rock matrix attached, you can add a few ounces of vinegar to the soap and water solution and leave the garnets to soak for a few hours. Then scrub away any remaining dirt and stains with a toothbrush and wash the stone with the cloth.
TIP: It’s challenging to differentiate between fake and real garnets without gemological equipment. Check out the main differences between real and fake garnets in the article below:
How To Cut Raw Garnet
Check out these six simple steps on how to cut raw garnets:
Assemble your equipment. You will need a chopping board, tap water, a tea towel, and four sheets of wet-dry sandpaper – one hundred and eighty grit, four hundred grit, six hundred grit, and twelve hundred grit. Examine your garnet to see how best to shape and cut it and where the facets should be located.
Perform the garnet into the desired shape and grind out any unwanted inclusions in the raw stone. Use the coarsest grit sandpaper first. Lay the tea towel on the work surface to prevent slippage and attach the sandpaper firmly to the cutting board with the rough side up.
Place the cutting board on the tea towel. Put a few drops of water in the middle of the sandpaper. Rub the edges of the garnet over the surface of the sandpaper until it is the shape you want, grinding away any rough edges and flaws.
If your garnet has some flattened sides already, rub each of them back and forth against the sandpaper to smooth them and bring them out more. Alternately, use the sandpaper to create some facets. Rub each facet flat against the paper.
Remove the one-eighty grit sandpaper from the chopping board and affix the four hundred grit sandpaper. Rinse the garnet in water to remove the grit and dust from the previous sandpaper. Put some water in the middle and rub each facet of the garnet repeatedly back and forth against the sandpaper.
Repeat step four for the six hundred and twelve hundred grit sandpaper. Don’t forget to rinse the garnet before moving on to a finer grit, and be sure to wet the middle of each sheet of sandpaper. Remember to grind all of the facets of the garnet using each grit size.
You can rub the garnet in a circular motion on the sandpaper now and then to ensure a smooth surface and edges.
Polish the stone using denim cloth and some polishing compound.
BTW: Do you want to know more about rock and mineral identification? The books listed below are the best ones you can find on the internet (Amazon links):
- Smithsonian Handbooks: Rocks & Minerals
- Gemstone & Crystal Properties (Quick Study Home)
- Ultimate Explorer Field Guide: Rocks and Minerals (National Geographic Kids)
Cutting Garnet With A Dremel
Dremels come with many attachments that can be used for cutting and polishing a garnet. You can use the engraver attachment to cut your garnet, but first, practice your technique on a hard, smooth pebble. You will need a vice, clamp, or dop stick to hold the garnet while you cut it.
Using a fine tip marker, draw the shape you want on the stone. Dremels with variable speed settings are preferable to only a single-speed tool. Starting at a slow speed, pull the tip of the bit along the lines you have marked evenly and without hesitation.
If you allow the bit to remain in one spot for too long, it will make a deeper cut within the line, making it uneven. Faster speeds remove more of the stone, making it easier to make a mistake.
TIP: The best tools for polishing rocks and adding a soft glimmer are the rotary dremels. Check out the best dremels in the article below:
How To Polish Garnet At Home
Once you have finished cutting, smoothing, and shaping the garnet, rinse it off and dry it. You can then polish it by rubbing it briskly on a piece of denim cloth, felt, or leather. When you have rubbed it as shiny as possible, you can apply some polishing agent to the fabric and rub the stone for that extra shine.
You can buy polishing agents such as aluminum oxide, cerium oxide, tin oxide, or silicon dioxide from rock shops. Some say that aluminum oxide works best for garnets.
Polishing Garnet Stones In A Rock Tumbler
Many garnets aren’t worth polishing in a tumbler because they have too many fractures or pits and may crumble.
Before tumbling, examine the stones closely for any fractures or significant inclusions as they will only get worse in a tumbler. If you have some robust, good-quality specimens, you can give it a try.
You can polish garnets in the tumbler together with jasper or agate, starting with a medium grit and working up to the finest.
Garnets are usually small stones, and you are unlikely to have enough of them to fill a tumbler unless you have bought some in bulk specially for tumbling. Use TXP aluminum oxide for the final polish.
TIP: Buying a rock tumbler can be a daunting task to a beginner. Check out the ultimate buying guide on the best rocks tumblers in the article below:
Polishing Garnet Stones With A Dremel
Once you have cut and ground your garnets to the right shape and size, wash them and dry them. Use the polishing or buffing attachment to bring them to a shine.
This attachment looks like it has a small piece of felt on the end. You can dip the polishing wheel in a polishing compound and leave it there for a couple of minutes with the Dremel running to ensure it is adequately coated.
Apply the polishing compound to the garnet’s surfaces with the Dremel. It’s best to hold the garnet in a vice or clamp when using a Dremel.
Cutting and polishing a garnet is not hard and can be done at home using sandpaper, a cutting board, and some water or a Dremel.
Polishing garnets in a rock tumbler is possible, but only if they are tumbling grade because many garnets have fractures and inclusions that make them unsuitable for tumbling. You can use a polishing compound and a piece of denim or the Dremel polishing wheel for the final shine.
TIP: Garnet is a highly valued gemstone. Do you know what makes garnet so valuable? Check out the explanation in the article below: