Silk

Silk is an item used in Dragon Slayer quest to open a door in Dwarven Mine. It can be bought for only 2 coins from the silk trader in Al Kharid, or with 20 thieving it can be stolen from the Silk Stall for 24 thieving experience.

Shops
Silk can be bought from these shops starting at 30 coins:

Trivia
Silk cannot be sold to the Al Kharid General Store because of the silk trader's presence in the town.