Amethyst, a purple-coloured variety of quartz, was first discovered near the shores of Lake Superior between the Ouimet Canyon and Thunder Bay in the middle of the nineteenth century. It is still mined hereabouts and specific deposits have been turned into well-signposted tourist attractions; Hwy-17 whizzes past a string of them. One of the best is Blue Points Amethyst Mine (mid-May to mid-Oct daily 9.30am–4pm), 58km east of Thunder Bay. Tours of the open-pit mine are free, but you can pick up a bucket and digging tool to gather as many lumps of rock as you want, and pay a minimal amount for your booty on the way out. Amethysts can be polished with baking soda.