Gold mining provided an important boost for the market in shares. At first most gold was extracted through alluvial mining in rivers, where miners could work as self-employed individuals without much capital. But once mining required tunnelling and railways to extract the quartz in which the gold was found, it needed capital investment. So mining companies began to attract funds through shares. The Invincible mine at the head of Lake Wakatipu was a relative latecomer – it opened in 1888, about 20 years after the first quartz mines.