Phyllite: 560 million years in the making

Phyllite is a type of metamorphic rock, that forms when shale is subjected to incredible heat and pressure for hundreds of millions of years underground. The resulting material is an outstanding natural stone that’s perfectly suited to roofing, flooring, cladding and much more.

Harder, denser and stronger than slate, or any of its other competitor materials, phyllite nevertheless splits easily during processing, and the mica particles on its surface give it an unmistakable ‘phyllitic sheen’.

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Phyllite thrives under pressure

Phyllite is the result of similar geological processes to the ones that produce other natural materials like slate – except phyllite undergoes even higher temperatures and greater pressures. That causes the clay present in the material to break down and form mica, which is responsible for phyllite’s satin-like lustre.

University of Bristol

University of Bristol

The finest phyllite, sourced from South America

Phyllite is extremely rare – much more so than slate. But at SSQ, we’re lucky enough to own one of the finest phyllite quarries in the world – San Luis, in La Repressa, Argentina.

It’s here that we source our exclusive Riverstone phyllite, put the extracted material through the most rigorous quality checks, before distributing the very best of it to customers all around the world.

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Slate vs Phyllite: What’s the Difference — and Which SSQ Range Is Right for Your Project?

If you’re weighing up slate vs phyllite for a roof, it helps to start with the fundamentals: phyllite sits between slate and schist on the metamorphic “spectrum,” which is why its texture and surface character can look subtly different in finished installations. For a simple overview, see [What is Phyllite?], then explore how it performs in the real world with SSQ’s two phyllite ranges — Riverstone andMontegris— to compare tone, riven character and suitability for your project brief. If you’re still undecided between alternatives, the SSQ slate comparison page is the quickest way to shortlist the right material and finish before requesting samples or a specification.

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montegris
Aerial view of intersecting grey slate roofs on red-brick buildings, showing terracotta ridge tiles and a metal chimney, with a courtyard and outbuildings below

Phyllite for Heritage Roofs: A Credible Alternative When Indigenous Slate Is Hard to Source

When working on heritage or conservation projects, sourcing a like-for-like indigenous slate can be challenging — whether due to availability, lead times, or the need to match existing roof character. Phyllite can be a practical option in these situations, offering a natural stone appearance that sits between slate and schist on the metamorphic spectrum. If you’re new to the material, start with What is Phyllite? for a clear overview, then read Heritage buildings: consider phyllite to see why it’s increasingly specified for heritage roofs when traditional sourcing constraints apply.

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Testimonials

We specified SSQ First Domiz Blue-grey roofing slate for both technical and aesthetic reasons:its strength and quality gives the performance needed and its cold, hard, colour provides a dramatic foil to the rich warmth of the western red cedar walls.

Mark Webber, Architect, Nichols Brown Webber

Testimonials

SSQ Ultra Del Carmen slates come with a 75-year guarantee and that was important. Not only that, the on-site services promised – and delivered – by SSQ enabled a smooth and easy workflow.

Stuart Howes, Architect

Testimonials

The quality and strength were there, the colour was similar to indigenous Welsh slate and its ‘traditional’ look was in keeping with the surrounding community. In fact, as I had used it on my own Edwardian house, I knew it was a good slate!

Julian Bohling, OSP Architecture

Testimonials

Everyone liked Sarria: the client was delighted with its appearance and its consistency made it easy to cut and lay.

Gary Lambert, Complete Roofing Contractors

Testimonials

SSQ Matacouta slate was chosen as the most sympathetic option. Its consistency and competitive price make it a clear winner over indigenous slates.

Historic Scotland

Testimonials

With so many ‘interested parties’ the local planners set their minds on a natural slate roof at a very early stage of the project and, from this starting point, we needed something that would satisfy a number of technical and aesthetic requirements – SSQ Domiz blue-grey, was the one chosen for use to compliment the local ‘Shere Green’ colour.

Ben Hunt, Total Project Integration

Testimonials

It was an absolute pleasure to meet you today, and I just wanted to take a moment to thank you for your time and a wonderfully informative CPD.

The whole team really enjoyed it, and you definitely conveyed your passion and knowledge of your products!

I would say I will keep SSQ in mind for future projects, but they always have been. However, I have definitely left with a need to utilise more slate in my design work!

Michael Clifton BSc ACIAT - Oakbridge Bespoke Homes Ltd

Testimonials

The choice of SSQ Del Carmen was made easier after confirmation that it had gained approval for use in the Welsh National Parks as an alternative to indigenous materials. We were also pleased with the level of technical, design and on-site support we received from SSQ.

The Hafod Renewal Office

Testimonials

Working in a conservation area brings a special responsibility. SSQ Riverstone slate fits perfectly, its tone and texture blending seamlessly with its surroundings.

Joan Kinane, Architect

Testimonials

SSQ Rocaber Blue-grey slate was actually chosen at the initial design-concept stage. A natural slate roof was in keeping with the traditional local architecture.

Tom Ewan, Architect at Model Developments

Testimonials

With the roofs being such a visible feature, the choice of roofing slate was a significant decision. We involved the roofing contractor at an early stage in the selection process and they recommended SSQ’s Del Carmen Blue-black slates. Although it’s not an indigenous slate, it is an excellent match for the originals and, having used Spanish slate on other projects, we know the quality is there.

Richard Thorpe, Ridge and Partners LLP

Testimonials

The choice of slates was made easier due to the quality of product you provide and the support of Gary Firth throughout the process – which I much appreciate. Gary is a good ambassador for your company.

Pat Murray, Senior Project Engineer, Alvance Group

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Case Study

Riverstone helps restore heritage charm to Russell Street School

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Case Study

Riverstone brings new life to historic Otter Valley landmark

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Case Study

SSQ’s Riverstone delivers award-winning restoration for iconic Cornish church

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Case Study

SSQ’s exceptional slate contributes to award-nominated heritage restoration

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Case Study

SSQ’s Riverstone provides reliable roofing solution for a piece of Cornish mining history

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