Granite boots are a pair of boots worn by Dondakan, a key character in the Between a Rock quest. He uses them in order to try to kick down the wall blocking the Arzinian mines. Although Dondakan will take offers on his boots, he will never sell them.
Trivia
In 2006 there was a rumour that because Dondakan was asking players to offer him "gold" that gold ores or bars may be what he wants, but 50,000 of each were offered and still he refused.
In early 2008 there was another rumour that he wanted "gold" armour (gilded armour), yet Dondakan still did not sell the boots.