How can I obtain oxygen gas from plagioclase
Yes, I collect oxygen isotope data from plagioclase using the laser flourination method. To liberate the oxygen from the plagioclase, crystals are reacted with purified $\ce{BrF5}$. Then the plagioclase is hit with a $\ce{CO2}$ laser. Gasses are sent through a couple of cryogenic (liquid nitrogen) traps to filter, and then through a mercury diffusion pump to remove that nasty flourine.