Copper extended its historic four-day rally to $10,000 per tonne on Thursday, helping boost tin to a new record in the process, as curtailed supply growth at a time of healthier demand continued to power prices higher. COMEX copper for March delivery peaked at a record $4.58 per lb, before settling up 0.05 cent at $4.5445. But without a meaningful price correction during this latest bull run, some market players voiced their concern over its sustainability.