Material with fairly high resistivity, but allows flow of charge Is there a material with fairly high resistivity (at least semi-conductor level), but also allows the flow of charge through it (and subsequently to the ground)? The flow of charge does not need to be fast, it can be very slow if necessary. The higher resistivity, the better.
So ideally, if that material is left alone on the ground, its steady-state should have very little charge, and thus have negligible or zero electric field (even if you initially applied some charge to it). Basically, the material is able to be discharged in finite-time, regardless of its fairly high resistivity. 
The speed of discharge is the property I'm particularly interested in, but based on what I've seen, this property might be independent of resistivity.
I am not sure if such properties are documented, so if you know what the property is called, please tell.
Thanks
Edit: My wording is apparently confusing, so let me try to put it in other words. Here is a phenomena I have observed. There is a piece of rubber and a piece of glass on the ground, both equal in size and resistivity. I apply a static charge to both, and the rubber ends up discharging (to ground presumably) much faster than glass. What is that material property called?
 A: The two main properties that determine the speed of discharge of a conductive object are capacitance and resistance. 
The product of the capacitance and the resistance, a time constant, could be used to ballpark the discharge rate (which follows exponential decay curve) and discharge time.
It is fairly straightforward to determine, when you have a discrete capacitor discharging though a discrete resistor. 
It is more complicated, if you have a distributed capacitance and a distributed resistance, like in a human body or an anti-static mat (an example of a material you are asking about at the beginning of your post).
If you have a particular object grounded in a particular way, you can measure its time constant by charging it to a particular voltage, then grounding it (and the way you ground it may affect the result) and then monitor the voltage on the object as it discharges using a field meter or a voltmeter (if the resistance of the voltmeter is much higher than the effective resistance of the discharge path), minding that, for high resistivity objects, the voltage will be different at different points.
The time constant of your setup will be the time it takes for the voltage to drop by about 63%. 
