The iShares U.S. Basic Materials ETF (IYM) is seeing unusually high volume in afternoon trading Tuesday, with over 736,000 shares traded versus three month average volume of about 74,000. Shares of IYM were down about 1.5% on the day.

Components of that ETF with the highest volume on Tuesday were Freeport-McMoran (FCX), trading down about 3.5% with over 13.1 million shares changing hands so far this session, and Dowdupont (DWDP), off about 2.2% on volume of over 9.2 million shares. GCP Applied Technologies (GCP) is the component faring the best Tuesday, up by about 2.1% on the day, while Compass Minerals Intl (CMP) is lagging other components of the iShares U.S. Basic Materials ETF, trading lower by about 17.7%.