The vast majority of slates used in Europe come from either Spanish or Welsh mines and quarries. Spanish slate such as the SSQ produced Del Carmen slate are some of the highest-ranking slates on the world slate index and are subject to rigorous quality testing procedures. Welsh slate mined from the Penrhyn, and Blaenau Ffestiniog areas of North Wales are also world renowned but due to overmining, are now extremely rare and subsequently very expensive.

The reputation of South American slate

For many years, South American slate has been viewed as a substandard material compared to European slates. Whereas Spanish, Welsh, and Cornish slates are formed from millions of years of geological processes involving heat and pressure (metamorphic rock), much South American slate is manufactured from sedimentary rock (rock formed through only pressure).

The European standard for roofing slate BS EN 12326 only applies to slate that has been manufactured from metamorphic rock. Therefore, the quality of South American slates cannot be tested to the same standards. This has led to a debate, particularly focused on Brazilian slates which are manufactured from sedimentary rocks. In some instances, Brazilian sedimentary slates have performed well over time while in other instances they have delaminated and failed. A universal testing process is now required to ensure consistency of quality in the South American slate market.

Argentinian phyllite vs Brazilian slate

Dundurn Walk

At SSQ, we are proud of our reputation as slate specialists. Our Spanish Del Carmen slates rival Welsh slates for both performance and appearance and have been used in installations across Europe. We were initially cautious when we discovered Riverstone – the Argentinian phyllite, which is stronger and more durable than slate. However, following years of in-depth research and testing, we decided to buy the Argentinian operation where Riverstone phyllite is mined.

When compared directly to Brazilian slate, Riverstone outperforms Brazilian slate in every criterion. Riverstone, like our Spanish slates is created from metamorphic rock whereas, as mentioned above, Brazilian slate is manufactured from sedimentary rock. Riverstone is therefore more rigorously tested and accepted in European roofing markets. Riverstone also has a far more attractive finish than Brazilian slate with its phyllitic sheen adding beauty to any installation. Riverstone is also far more durable. With a life expectancy of over 100 years and a weather resistance capacity which far outweighs Brazilian slates, it is easily the best option.

Riverstone in the UK


At SSQ, we have now shipped thousands of pallets of Riverstone phyllite to the UK ready for distribution. It has proven extremely popular in the UK roofing industry and has now been used as an alternative to slate in many roofing projects.

If you’re looking for slate for a roofing project, our expert advice would be to use a traditional Spanish slate like Del Carmen or try a slate alternative such as Riverstone. While some South American slates may provide high performing protection, the current European standards don’t recognise them, and you may struggle to gain the required permissions.

If you have any questions related to our slates, get in touch today. Call 020 8961 7725 or contact us online.

Sign up to our newsletter

Subscribe to our newsletter to keep up to date with the latest news and offers.