This is the most important article on this site. Everything else is about making better work. This is about still being able to work in twenty years.
What silica does
Crystalline silica is a mineral compound present in most stone. When you cut, grind or chip stone, some of the dust produced is fine enough to reach the deepest parts of the lung — respirable particles, far too small to see, which stay airborne for hours and lodge where the lung cannot clear them.
The damage is cumulative and irreversible. It does not announce itself early, and by the time symptoms appear, the change to lung tissue is permanent. There is no treatment that reverses it.
Which stones are worst
The silica fraction varies substantially by stone type, and the difference matters for how you work.
| Stone | Silica content | Risk | Working guidance |
|---|---|---|---|
| Granite | Very high (~30 % quartz) | High | Wet cut; P100 mandatory dry |
| Sandstone | High (~90 % quartz grains) | High | Never dry-cut indoors |
| Slate | Moderate to high | High | Wet cut preferred |
| Marble | Low (calcite) | Medium | Wet cut; P100 for dry work |
| Limestone | Low (calcite) | Medium | Wet cut preferred |
| Soapstone | Variable, may contain tremolite | Medium | Extract and mask regardless |
| Alabaster | Very low (gypsum) | Low | P2/P95 still advisable |
The three controls, in order of effectiveness
- Eliminate the dust — work wet. Water at the cutting point can reduce airborne dust by roughly 90 % on most operations, and it also cools the tool and extends its life. On any stone that tolerates water, this is the first and best answer.
- Extract at the source. A HEPA H13 or M-class extractor with a capture hood positioned as close to the cutting point as possible. An ordinary workshop vacuum with a cloth bag makes things worse, not better — it filters poorly and exhausts the fines straight back into the room.
- Protect the operator. A fitted P100 half-mask for any dry operation. Fit is everything: a mask that leaks at the nose delivers almost no protection, and facial hair breaks the seal. Do a fit check every time you put it on.
A respirator is the last line of defence, not the first. If your only control is a mask, you have not controlled the dust — you have moved the problem to your face.
The things people get wrong
- Dry-sweeping the workshop. This re-suspends settled dust and is one of the largest single exposure events. Wipe with wet cloths, or use a wet vacuum.
- Assuming soft stone is safe stone. Soapstone dust is fine, pervasive, and may contain tremolite. Soft does not mean safe.
- Taking the mask off for "just one quick cut". The dose is what matters, and short cuts add up.
- Leaving a mask on a dusty bench. A mask stored in a dusty workshop is a dusty mask.
- Emptying the extractor indoors without a mask. This releases a concentrated cloud.
“Use a mask and safety glasses. Consider wet carving — with water there is essentially no dust, and tool life improves because the bits stay cool.”
The rest of the PPE list
Silica is the defining hazard, but it is not the only one. Chisel work throws fragments, and a bush hammer throws them hard.
- Sealed goggles with indirect ventilation — not ordinary safety glasses, which do not keep dust out.
- Hearing protection for pneumatic tools, which run at 95–110 dB(A).
- Gloves for handling stone and abrasive slurry, and for solvent-based sealants.
- Steel-toe boots. Stone is heavy, and a dropped block does not bounce.
- A fitted respirator with a scheduled filter change, not one you replace when you notice a taste.
