What are the gold bits in my slate? Will they form a hole?
The gold crystals are likely to be pyrites, a type of metal inclusion that is present in all natural slates, but not always visible.
Some pyrites may cause staining or even holing. However if your slate is a SIGA Natural Slate it will have been tested to BSEN 12326 and achieve the best classification “T1”.
This states that any metallic content (pyrite) should not form runs of rust or staining, and any visible pyrites should not form holes.
Ensure your natural slates are always classified T1 by choosing SIGA Natural Slate.
Read more about Markings on Roofing Slates.