Gold dust is a slang name for MDMA powder (ecstasy). MDMA is usualy in the form of tablets, and MDMA is almost never seen as a powder for several reasons;
  • MDMA is almost as active orally as it is nasaly (unlike cocaine), so it is not wasteful to take it as tablets
  • It is significantly easier to consume tablets than powder
  • MDMA is rather unpleasent to snort (the prefered method of taking powdered drugs) or gum-rub.
  • Low doages are more important for MDMA than for amphetamine and cocaine (two drugs that are often taken as powder), as it is active at lower levels, and the side effects of large doses are unpleasant.

However, some people consider taking MDMA to be a much more enjoyable experience when it is snorted as a powder, and to them MDMA powder is something of a holy grail. It is presumably called gold dust because of its rarity and desirability