Chemical elements or alloys, their ores, and the mines where their ores come from.
Most of the matter in stars is hydrogen and helium, and the metals (including carbon, nitrogen, oxygen, and so on) were cooked up inside stars.
2008, Lunar and Planetary Institute, Geochemical Society, Oxygen in the solar system, Mineralogical Society of Amer →ISBN
Thus, for the remaining elements, including oxygen, the solid phase appears to be important. In fact, at a metallicity of Z=0.02, and with a gas-to-dust ratio of 100, about half of the metals — including oxygen — are contained in the solid phase.