Copper slid to a six-week low on Tuesday, hit by a strong dollar and lack of robust demand from top metals consumer China as the market gave up more gains from its September rally. Three-month copper on the London Metal Exchange traded at $7,860 a metric tonne in official rings, down from $7,953 at the close on Monday. Earlier it dropped to an intraday low of $7,859.5, a fresh low since September 7.