I visited the amber mines on my own, actually -- it's no problem if you don't mind driving there. Its off the Carretera Turistica, I think 13km north of Santiago near a village called La Cumbre. If you need help, stop at this great restaurant off the highway called Cemi, who take people to the mines sometimes if they're staying at their bungalow. Otherwise, look for a turnoff that says La Cumbre de Juan Vega and head west for a kilometre or maybe a bit more. They're really little more thay gerry-rigged holes in the ground with wooden supports, but the miners are extremely nice and will offer to sell you bits of the stuff.