Natural slate stone, the material used for engraved slate coasters

Is Slate Sustainable? The Honest Environmental Case for Quarried Stone

Slate is sustainable in some ways and not in others. It needs very little processing compared with other hard materials, so the carbon used to turn it into a finished product is low, and it lasts for generations. But it is not renewable, quarrying it has real local impacts, and there is no chain-of-custody certification for stone like FSC's. Its strongest environmental argument is that it rarely needs replacing.

Quick answer

  • Low-carbon to process? Yes. Natural slate is split and cut rather than fired or manufactured.
  • Renewable? No. It is rock formed over millions of years.
  • Quarrying impact-free? No. Blasting, dust, noise, water use, waste rock and habitat loss are real costs.
  • Certifiable like FSC wood? No. FSC covers forest products only.
  • Biodegradable? No, but it is inert, and waste slate can be crushed for aggregate.

What slate is

Slate is a metamorphic rock formed when clay-rich sediment or volcanic ash is compressed and heated over millions of years. That separates it from the other materials we use: oak, birch and bamboo regrow, and slate does not. Every piece quarried comes from a finite deposit, so "sustainable" for slate can't mean renewable. It has to mean low impact to produce and long life in use.

The low-carbon case

Natural slate is split along its natural cleavage and cut to size, with no kiln firing like clay tiles and no cement like concrete tiles. The Inventory of Carbon and Energy (ICE) from the University of Bath, version 1.5 (2006), gave natural slate 0.005 to 0.054 kg of CO2 per kilogram, against 0.19 for concrete tile and 0.43 for clay tile; version 2.0 (2011) put slate at 0.006 to 0.058. Those figures are now old, the current edition of ICE no longer lists slate, and they are mostly quoted by slate sellers, but the direction is clear: slate needs far less energy to process than fired or cast alternatives.

The figures cover production, not transport. Slate is heavy, so where it was quarried and how far it travelled matter, and the ICE range is wide partly for that reason.

The cost of quarrying

Quarrying any stone involves blasting or cutting rock, heavy machinery, dust, noise, water management and large volumes of waste rock, and it changes the landscape and habitats around the quarry for a long time. Historic slate quarrying left tips that still dominate parts of North Wales. None of this cancels the low processing figure; it is simply the part that carbon-per-kilogram numbers leave out.

Certification: the honest gap

For our FSC-certified Moso bamboo (certificate BV-COC-190523) and FSC-certified oak veneered MDF, chain-of-custody certification gives a checkable answer to where the material came from. Nothing equivalent exists for quarried stone. Larger slate producers serving the building trade may hold ISO 14001 environmental management certification or publish Environmental Product Declarations (EPDs) to EN 15804, and in the United States the ANSI/NSC 373 standard certifies sustainable production at dimension-stone quarries. These are uncommon for small decorative slate. We have not found a small-format slate supplier, including ours, that holds a third-party environmental certification for its product, so we make no sustainability claim for our slate and describe it simply as natural slate.

Where slate's real case lies: it doesn't wear out

Slate roofs commonly last a century or more, and a slate coaster used normally will outlast most households. The most sustainable product is often the one that never needs remaking, and slate's durability is a genuine reason to choose it, not a marketing line.

At end of life slate is chemically inert: it doesn't rot or biodegrade, but it doesn't leach anything into soil or water either, and waste slate is routinely crushed and reused as aggregate.

A note on scale

The carbon figures above come from building-scale studies of roofs and tonnes of material. We have not found published data for a single 100mm coaster and won't pretend the roofing numbers translate exactly. What holds at any scale is the pattern: low processing energy, real extraction impacts, very long life.

Our slate products

We engrave natural slate coasters, with your own text, a logo, or a QR code for reviews or social media: see the personalised slate coaster, custom logo slate coasters, Google review slate coaster and the full coasters collection.

Ordering from us

Everything is engraved to order in our workshop in North Wales. Choose a product, add your wording or logo where the listing offers it, and add to basket. Bulk discounts apply automatically at checkout, per product: 10% off 20+, 15% off 50+, 20% off 100+, 25% off 250+, 30% off 500+ and 35% off 1,000+.

All items are made to order. Dispatch time is shown at checkout. UK orders via Royal Mail Tracked 24. International via Royal Mail International Tracked.

Frequently asked questions

Is slate an eco-friendly material?
Partly. Processing slate uses little energy compared with clay or concrete tiles, and it lasts for generations, but it is not renewable and quarrying has real environmental impacts.

Is slate renewable?
No. It is rock formed over millions of years and cannot regrow.

Can slate be FSC-certified?
No. FSC covers forest products only. Some large stone producers hold ISO 14001, publish EPDs or are certified to the US ANSI/NSC 373 quarry standard, but there is no chain-of-custody scheme for stone like FSC's.

Is slate biodegradable?
No. It is chemically inert, so it doesn't break down, but it doesn't leach anything either, and waste slate can be crushed for aggregate.

Does your slate carry an environmental certification?
No. We haven't found a small-format slate supplier, including ours, with a third-party environmental certification, so we describe it simply as natural slate.

Sources

Also see: our materials and sustainability page, what FSC chain of custody means. For branded coasters, see oak, bamboo or slate logo coasters for business.

Back to blog