Ask the manufacturer (not the supplier), some say yes some say no. It doesn't really matter where they come from, only one company (Breton) make the machine that produces this product. So the only thing that can differ is the constituent products put into that machine.
Dave highlights a common misconception with Quartz about the resin content.
The most expensive component in the manufacturing of quartz tile and slab is actually the resin and pigment (basically anything oil based) that generally makes up around 7% of the total content of a "starlight" type quartz. The other 93% being made up of quartz grains of varying sizes and glass chipping that give the mirror effect.
The more pure the colour the higher the resin content. So a Pure white could be as much as 15% resin. That's why the pure colours are so expensive when combined with the number that are rejected due to colour contamination during production.
The higher the resin content, the more expensive the product. Think of Corian and other solid surfaces which are substantially more expensive again than Quartz.
If anything, the cheaper products will have less resin, not more as that reduced production costs. It's the resin that binds the structure together, think if like the egg when you're making pastry. Too much or too little egg and your mixture is all wrong.
As a floor tile I rate granite above quartz by a country mile. As a decorative product, quartz is outstanding.
I used to manufacture quartz slab, the list of disclaimers you're required to give with this product would make you wonder where it could be used at all. Couldn't be stored outside, had to be stored away from UV light, cannot be used externally, not frost proof etc etc etc
However, it's down to each manufacturer if their product is suitable for UFH. I know Technistone say theirs is. I've not kept up with the others lately.
Silestone is the market leader worldwide in Quartz products, they are generally accepted as the best quality producer.
Reading the terms of their 10 year guarantee is an eyeopener.
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