Plots lifted straight from a paper don't always look great on screen. Here are some important plots from my recent papers reformatted for presentations. Feel free to use them.
None of the 849 F, G, and K dwarfs in this sample of planet search stars has C/O > 0.7. This distribution is in agreement with galactic chemical evolution models and means that the likelihood of finding diamond planets is quite low. It does, however, mean that the Mg/Si ratios of these stars can tell us about the geology of any rocky planets in the system.
Previous studies have shown a correlation between metallicity (as measured by [Fe/H]) and the C/O ratio. Our sample largely agrees at [Fe/H] < -0.1, but seems to flatten out for more metal rich stars. This also agrees with galactic chemical evolution models that expect C/O ratios to plateau.