I meant, pre-impregnate the quartz particles with your mineral oil.
If investigating the option of additives, you could have a look at the ones used for synthetic hydraulic fluids like polyethylene glycol, phosphates... These ones, not obtained from crude oil, are less good at wetting so they become often additives to improve that.
Did you consider pure biodiesel as the oil? Its ester part would be more compatible with an oxide ceramic than a hydrocarbon is.
You might also give a try to other oils like polyethylene glycol-based ones. If water wets your quartz quickly, it's an indication in favour of these watery fluids.