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How to Cut and Polish Agates? Follow These Simple Steps

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Agates look quite dull from the outside. It is when they are cut and polished that their intricate wavy patterns and colors are revealed. Agates can be cut into slices – perfect for wearing as jewelry – or they can simply be cut in half, as a beautiful specimen for your rock shelf. 

Agates can be cut using a slab saw, band saw, table saw, or Dremel tool. Use a vice grip to hold the rock in place and push it towards the blade as it is being cut. After cutting, agate can be polished using a rock tumbler and polishing powder, sandpaper, or a sanding wheel.

Cutting and polishing agate takes a long time because it is such a hard rock, but the results are absolutely worth it. Agate is renowned amongst gem collectors and rockhounds for its vibrant colors and patterns. Cutting and polishing should be done in a way that showcases a particular agate’s unique characteristics. 

If you are interested in checking out the best Dremel drills or saws for cutting agates you can find it by clicking here and here (Amazon links). And if you are interested in checking out the best rock tumblers for tumbling agates click here (Amazon link).

How to Cut and Polish Agates? Compete Guide for Different Options and Tools
How to Cut and Polish Agates? Compete Guide for Different Options and Tools

Before You Start: Properties of Agate

Agates are quarzitic rocks, comprised of crystalline silica. Impurities, such as iron oxide or pyrite, present in the surrounding geology gives agates a wide variety of colors – red, yellow, purple, grey, white, green, blue, and many hues in between. 

Agates form within cavities in rocks. A silica-rich solution fills a nodule or cracks in the rock, and over time starts to deposit crystals on the walls of the cavity. This process happens very slowly, one molecule at a time, and forms a dense, fibrous microcrystalline quartz structure

As impurities from the surrounding parent rock make their way into the crystal lattice, they color the agate, and in some cases, cause circular or layered banding to occur. This is what gives agates their characteristic patterns.

When agate is free from any impurities and is transparent and colorless, it is referred to as chalcedony. If there are larger amounts of impurities, and the rock is opaque and multi-colored, it is referred to as jasper

We need to consider the properties of agate before cutting them, as the idea is to bring out the best in rock. To best showcase a specimen’s concentric banding or colors, one needs to examine the rock carefully to see the direction of the pattern and decide where to make the cut. 

Do You Need Lapidary Equipment to Cut Agate?

On the Mohs Hardness Scale, agate is a 7 out of 10, meaning that it is a very hard rock. This makes sense, as it is quarzitic. Does this mean you will need professional lapidary equipment to cut it? 

Professional lapidary equipment, like slab and trim saws, is not necessary to cut agate unless you are wanting to carve fine facets or intricate shapes. Having professional equipment will, of course, make the job of shaping and polishing easier.

But you certainly can get away with using a bandsaw or table saw with a diamond-tipped blade, especially if you are just wanting to make a general cut to expose the inside of an agate. Many rockhounds use a Dremel tool with a diamond-tipped bit to cut agates.

Best Blade for Cutting Agate

Agate is a very hard rock so a diamond-tipped blade must be used to cut it. In terms of safety, it is best to use a power saw blade that is at least 0.006 inches (0.015cm) thick.

Blades this thick are less likely to cut your finger. Nevertheless, use extreme caution when using any type of saw!

Which Way to Cut an Agate

Carefully inspect an agate before deciding how to cut it. With agates, it is best to allow the rock to guide the shape and not to force it. Cut along the agate’s natural features.

Wet the agate and inspect it under a bright light. Look for wavy layers and decide how best to cut the stone to showcase them. 

Agates can be cut into slices about 0.2 inches (0.5cm) thick, to reveal their concentric, circular patterns and colors. This is a great option if you are using agate to make jewelry.

One can also cut agates straight through the middle, to create two pieces with the same sized faces. If it is difficult to determine what the middle of agate is due to its irregular shape, cut through the fattest part.

TIP: Speaking about rocks in general, one of the most common methods to cut them is using a hammer and chisel. Check out the step-by-step guide on how to cut rocks with a hammer and chisel in the article below:


Step-by-Step: How to Cut Rocks with Hammer and Chisel


Different Methods for Cutting Agate

There are many different methods for cutting agate. Which method you choose depends on the tools that you have at hand. You could use any of the following:

  • Slab saw. These are used in professional lapidary to cut large rocks into smaller, more manageable pieces that can then be cut or shaped further. It has two motors – one that powers the diamond blade and another that pushes or feeds the rock towards the blade.
  • Bandsaw or table saw. A bandsaw has a long, thin blade on a band that spins around through a worktable. A table saw has a circular spinning blade that is mounted in a worktable. This method is good for cutting rocks that are big enough to hold safely on both sides to feed into the blade.
  • Dremel tool. This versatile rotary tool can be used with a diamond wheel bit to cut agates that are too small to hold while feeding it through a power saw. The largest diameter stone that can be cut is 3 inches (7.6cm) as this is the largest size that Dremel blades come in.

Use a Slab Saw to Cut Agate 

Follow these 10 easy steps to cut an agate using a slab saw:

  1. Secure the stone in place by clamping it down tightly in the slab saw. Use a vice grip to tighten the thumb screws on the clamp, to ensure the stone cannot move around while it is being cut – this will damage the blade.
  2. Adjust the position of the rock in relation to the blade by toggling the clutch, to cut the rock at the correct point for the width of slab you want.
  3. Shut the lid of the machine.
  4. Switch the motor for the blade on first.
  5. Next, switch the feeder motor on, to start the stone moving towards the blade.
  6. Wait until the saw has cut through the whole rock. This usually takes between 5 and 10 minutes, depending on the size of the agate. 
  7. Stay close to the machine the whole time, listening for any strange noises that would indicate something has gone wrong.
  8. When the slab has been cut, switch the feeder motor off first. 
  9. Wait a few seconds and then switch off the blade motor.
  10. Wait a few minutes for the oil and slurry to drain before opening the machine and having a look at the cut.

Recommended: If you are looking for buying a slab saw I recommend checking this slab saw (Amazon link) made by Skil company. They are producing high-quality products for a great price.

Use a Bandsaw or Table Saw to Cut Agate

The method for using a bandsaw and table saw to slice agate is the same and produces equally good results. Follow these steps:

  1. Making sure the power saw is turned off and unplugged, remove the blade and replace it with a diamond-tipped saw blade
  2. Put on a dust mask and safety glasses to prevent the fine dust from the agate from entering your nose, mouth, or eyes.
  3. Plug in the power saw to an electrical socket and switch it on.
  4. Holding the agate flat against the table, with one hand firmly on each side, start to feed the agate into the saw blade.
  5. Ensure that there is at least 3 inches (7.6cm) between your fingertips and the blade. If the agate is too small to allow this, place the agate in a vice grip and hold this while you feed it into the blade.
  6. Keep the agate straight as you feed it into the saw blade. If it turns at an angle, it can damage or break the blade.
  7. Do not take your eyes off the blade while you are cutting.
  8. Keep pushing the agate into the blade, while holding it firmly against the table, until the rock has been cut through.
  9. Turn off the power saw and unplug it when you have finished cutting.

Recommended: If you are looking for buying a slab saw check out this band saw (Amazon link) made by Gryphon Corporation. The excellent performance of this saw is guaranteed by the diamond. But to be honest, if you are not going to cut rocks regularly, this saw is unnecessarily expensive for you and I recommend you use other, cheaper options for cutting rocks like dremels or slab saws.

Use a Dremel Tool to Cut Agate

Follow these steps to cut an agate using a Dremel rotary tool:

  1. Fit a diamond blade onto your Dremel tool.
  2. Hold the agate firmly in place by using a clamp mounted to a workbench. Ensure that the part of the agate being cut is exposed enough. 
  3. You can use a pencil to draw a line where you want to cut as a guide
  4. Put on a dust mask and safety glasses to prevent the fine dust from the agate from entering your nose, mouth, or eyes.
  5. Plug the Dremel tool in, set it to a moderate speed and then turn it on.
  6. Holding the Dremel tool with both hands, slowly and firmly press the blade into the agate.
  7. Slowly push the Dremel blade, keeping it straight at all times, into the agate until it had cut all the way through. 
  8. If the Dremel blade turns red from the heat, back it our of the cut slowly, turn it off and allow it time to cool down.
  9. If the stone is too thick to cut all the way through from one side, cut the one side, rotate the stone 180 degrees in the clamp, and then cut through from the other side.
  10. Turn off the Dremel tool and unplug it when you are finished cutting. 

TIP: Dremel is an amazing tool not just for cutting rocks but for rock polishing too. And the great news is that these tools are not too expensive. Check out the reviews of the best dremels for rock polishing in the article below:


3 Best Dremels for Polishing Rocks & Crystals + Accessories


Tumbling Agate

Using an electric rock tumbler for agates is extremely effective for removing the outer layers from the rough stones and polishing the rocks to bring out the best in their patterns and colors

Carbide grinding powder and water is added to the tumbler along with the rocks, and this helps to grind away the rough outer layer of the agate. The grinding powder comes in various grits – coarse, medium, fine and polished.

Agates are usually run through a rock tumbler for 7 days with each grit of grinding powder, but depending on the finish you are after, they can be tumbled for a shorter or longer period. This still means that tumbling and polishing agates can take weeks

Tumbling is usually done after the rock is trimmed and cut. However, when you want to cut many, even slices from a piece of agate, tumble the rough stone with polishing powder before you cut it. This will decrease the amount of polishing you need to do after cutting.

Polishing agate manually, using sandpaper and powdered polish is very laborious and time-consuming because of how hard the rock is. It is an okay method if you only have a few agates you want to shape and polish, but if you have many, it is simpler to use a tumbler.

How to Polish Agates in an Electric Rock Tumbler

Follow these steps to polish agates in an electric rock tumbler:

  1. Open the tumbler and put the rough or cut agates into the barrel
  2. Add coarse grinding powder to the tumbler.
  3. Fill the tumbler with water until all the rocks are covered.
  4. Run the tumbler for a week.
  5. Switch off the tumbler, remove the stones and clean out the water and sludge.
  6. Add the agates back to the tumbler, and this time add fine grinding powder.
  7. Fill the tumbler with water until all the rocks are covered and run the tumbler for another week
  8. Switch off the tumbler and remove the agates.
  9. Rinse them off in a colander.

TIP: If you are interested in buying a rock tumbler check out my recommendation for the best rock tumblers for the beginners and hobbyists in the article below:


Best Rock Tumblers in 2021: Beginner and Hobbyist Options


Polish Agate Slices with a Sanding Wheel

A sanding wheel can be used to polish agates by following these steps:

  1. Set the sanding wheel up with 150 grit sandpaper.
  2. Put on a dust mask and safety glasses to prevent the fine dust from the agate from entering your nose, mouth, or eyes.
  3. Turn the sanding wheel on and press the agate against it.
  4. When the piece of agate has the desired form, switch the wheel off and dip the agate in water to clean off the dust.
  5. Load 300 grit sandpaper onto the sanding wheel and switch it on.
  6. Press the agate to the wheel, rubbing it back and forth over the exposed surface of the agate
  7. Repeat this process, gradually increasing the grit of sandpaper (500, 800, 1000, 2500) and rinsing the agate in between.
  8. When you get to the 3000 grit sandpaper, add a little powdered polish to the sandpaper and use this to polish to agate to a brilliant shine
  9. Wash the rock and dry it with a clean, soft cloth.

Polish Agate Using Sandpaper

The manual way to polish agate uses sandpaper, water, and many hours. Follow these steps to polish an agate by hand:

  1. Place a piece of 150 grit sandpaper on a hard, smooth worksurface. 
  2. Wet the sandpaper with a few drops of water. Polishing the agate dry may scratch or chip the stone.
  3. Rub the agate back and forth on the sandpaper until you get the desired shape.
  4. Dip the agate in water to clean off the dust.
  5. Use increasingly finer grit sandpaper (300, 500, 800, 1000, 2500, 3000) to repeat this process until you have reached the desired finish. 
  6. Rinse the agate in clean water and dry it with a soft cloth.

BTW: Do you want to know more about rocks and minerals identification? The books listed below are the best ones you can find on the internet (Amazon links):

Conclusion

Agate is a very hard quarzitic rock that can be cut using a slab saw, band saw, table saw, or Dremel tool. These all need to be equipped with a diamond-tipped blade.

Hold the agate firmly against the table with one hand on each side of the blade or use a vice grip to hold the rock in place and push it towards the blade as it is being cut. It is important to keep it straight, to prevent damage to the blade.

Agate can be polished before and after cutting in an electric rock tumbler with grinding powder. To polish a cut piece of agate, one can use a sanding wheel, with increasing grits of sandpaper. One can also polish an agate manually using wet sandpaper. This takes a very, very long time due to agates hardness.

TIP: So you already know how to cut and polish agates, it’s time to find some agates! Find out the best locations for finding agates in the United States and the rest of the world in the article below:


Where Can I Find Agate Rocks? Best Places in the US & World