Copper continued it’s longest rally in a decade, rising 0.6 percent on Tuesday to hit $6,438, according to Bloomberg Business. This week, Glencore( LSE:GLEN), the world’s third-largest copper mining company, announced copper output from its mines slipped 9 percent last quarter. That drop compounds preexisting supply issues and coincides with an anticipated increase in Chinese demand.

According to Mike Dragosits, a senior commodity strategist at TD Securities in Toronto, “Glencore has added another layer to the tightening supply-side story.”

Comex copper for July delivery rose 0.4 percent to $2.933 a pound.