Appearance: Yellow to green to bluish-black, iridescent crystals ; Yellow-to-green-to-blue-to-black crystals, depending on purity ; Yellow to green to bluish-black, iridescent crystals.
Appearance: Colorless gas ; Odourless tasteless colourless compressed gas ; Colorless, odorless gas. [Note: Shipped as a nonliquefied or liquefied compressed gas.]