Mintaro slate was exhibited at the 1862 London International Exhibitions where it received the highest awards for large slab size and excellent flatness .
By 1860 Mintaro was South Australia 's leading producer of high quality slate .
Mintaro slate was exhibited at the 1862 London International Exhibitions where Mintaro received the highest awards for large slab size and excellent flatness .
By 1860 Mintaro was South Australia 's leading producer of high quality slate .