Eonyang amethyst

Eonyang, in Ulju county on the edge of Ulsan in southeastern South Korea, has been producing amethyst since the Silla period, which is to say for well over a thousand years. Around fifty mines have worked the ground, and Korean amethyst has a reputation for colour among people who know the material.

Amethyst is quartz coloured by iron and natural irradiation, and the deep even purple that Eonyang is known for is uncommon anywhere. That reputation is old enough to have had consequences: during the Japanese occupation between 1910 and 1945 the mines here were worked hard and a great deal of amethyst left the country illegally.

Commercial mining has finished, and what happened to the workings afterwards is the reason this is a pin worth having. One of the abandoned mines has been turned into Jasujeong Donggul Nara, the Amethyst Cavern Park: about two and a half kilometres of galleries running back into the hill like a maze, split into ten themed sections, lit, with sculptures, an underground boat ride and, inevitably, a dinosaur hall. It sits at twelve to fourteen degrees all year round, which in a Korean August is most of the appeal.

Be clear about what it is. It is a family attraction built inside a real mine, not a mineralogical site, and the crystal you buy in the shop is more likely to be imported than local. What is genuine is the tunnel itself, hand-driven through amethyst-bearing rock by people chasing colour, and you are walking in it.

Collecting is not on offer, at the park or on the surrounding ground, which is private and worked out. Go for the tunnel and the history, then look at Korean amethyst properly in the Gyeongju museums an hour up the road, where Silla goldwork puts it in its original setting.