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I'm looking for ideas on how to cut small raw gemstones (1" or less in diameter) in half without damaging the crystals and preferably without spending hundreds on a lapidary saw. I've been told tile saws and dremels aren't appropriate for this application. I've also been told the stone and blade must stay wet through the process.

Has anyone done this at home or have any ideas?

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    Specifically what sort of gemstones? Diamond is harder than anything else (and if you could afford to go cutting it up you could afford the tools to do so). Sapphire (including ruby) is almost as bad, but most others are softer. Table. A dremel probably spins too fast and isn't intended to be used wet; it may also waste to much with a thick wheel, but might be worth a shot on something cheap or scrap. – Chris H Feb 13 '17 at 16:53
  • I don't have an answer for you, but I took a stained glass class and we had to add water to the saw's basin before using it (here's a video of a similar saw: youtube.com/watch?v=6xKov3s_Vwc). Our instructor told us that the water reduced the heat that would build up from the friction of the blade against the glass, and could otherwise warp the blade. I wonder if you could use a glass cutter, scoring along the center line of the gemstone multiple times and then use breaking pliers to break it, just like you would with a piece of glass? – magerber Feb 15 '17 at 0:35
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    Scoring helps guide a break. If the gemstones are anything but flat this will be near impossible to do. So I do not think that will work well except in very specific circumstances. – Matt Feb 17 '17 at 14:35
  • Have you tried a diamond saw blade? I believe diamond is the only thing that cuts diamonds. – Terry Jeanne Feb 27 '17 at 23:03
  • Most gem stones aren't diamond, though. While sapphire is nearly as hard, emerald is quite soft. This is what Chris H mentioned in is comment. – Catija Feb 27 '17 at 23:05
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There are lapidary materials that can be cut without using specialized saws. Small raw gemstones are not good candidates, however.

Prior to modern lapidary equipment, cutting small gemstones relied on understanding, and taking advantage of, a stones natural cleavage. This method gives very little flexibility as to how and where you cut, and will result in a lot of lost material.

Tile saws, dremels, and end-cut bolt cutters can be used to cut gemstone material without the cost of specialized equipment, but all suffer from limitations.

End-cut bolt cutters: an example bolt cutter ...can, in a pinch (no pun intended!), cut slabs (sections of gemstone material pre-cut into relatively even thickness slices) to preform for cabochons, but they are most likely to just shatter anything that isn't a flat slab.

Dremels can be fitted with diamond blades to cut gemstone materials with finer precision, but they still have some serious downsides. The biggest concern is health: cutting stone materials generates dust, which if inhaled, can lead to silicosis, a dangerous and debilitating lung disease. Gem cutters typically mitigate this risk by always keeping material wet while cutting and polishing it. This keeps the dust within the water, and out of the air.

Dremels may also have difficulty cutting tougher materials, as unless you obtain a variable-speed tool (which tend to be more expensive), it will likely be too fast. Lapidary saws are designed to cut at a slower speed, to gradually wear away the material without cracking or shattering it, and to keep the blade from binding.

Tile saws also spin too fast for harder lapidary materials. They also tend to have a much larger kerf.

The kerf is the width of the actual cut, where the blade removed materials:

illustration of kerf in cutting

The larger the kerf, the more material is destroyed by the cutting process. When dealing with larger, inexpensive material, this may not be a big problem, but for small gemstones, this is likely to be a significant concern.

Ultimately, your best bet is to use specialized saws. Beginner hobby saws can be relatively affordable, especially if you can obtain one used. If there is a gem and mineral club nearby that you can join, some of them will have club machines available for members to use. Even if the club doesn't own machines, members might be willing to help you out. Just remember that the blades for the machines are expensive, and wear out relatively quickly. Offering some money to cover wear-and-tear would probably be appropriate.

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I would strongly advise to not just cut any gemstones without expert knowledge.

The issue is not just hardness but chipping. Different gemstones react very different to impact or stress and can easily break or chip.

One exception is amber for example because it's very soft and can be worked on without much risk of damage. Most stones are not that easy though. An extreme example for that is opal since they are very unstable and react badly to any kind of temperature changes that can occur while working on it.

You would need to know exactly how to cut every gem type (sapphires react different from tourmalines, both react different from citrine or amethyst,...) to minimise chipping or breakage.

So without knowledge of how the specific stones you want to work on react, keep your hands off them for risk of causing extensive damage.

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  • I regularly cut cuprite (too soft to be much of a gem despite the appearance) and sapphire (really rather hard), but also silicon, and many other crystalline materials, but also glass. With the diamond saw we have here, and protecting the workpiece with mounting resin, you can use the same settings for all of the above (because we stick to a slow feed-rate and always cut wet). This is an industrial rather than a lapidary diamond saw (>10x the price!) – Chris H Jul 11 '18 at 14:00
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Get a hardness chart for gems & stones, this can help you determine what blade to use. Dremel tools are great for cutting gems and stones of all kinds. They have diamond tips and more. They have cutting blades of all kinds. I use mine on gems and stones all the time. Many sites with jewelry stuff have charts on hardness. Google useing a Dremel to make jewelry you should find something

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    This reads more like an advert for Dremel tools than an actual answer to the question, as does your other post. – walrus Jul 26 '18 at 8:43

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