One more contributor to virgin vinyl...When firing up the equipment to make a pressing for a day's run, it takes dozens of pressing for the equipment to stabilize (temperature, pressure, etc.). These warm-up pressings, as well as other quality rejects, are ground up and the results are called re-grind. For non-virgn vinyl, there is some percentage of re-grind (and resultant impurities, like lable paper, dust, etc.) that goes into the hopper with the virgin pellets. Virgin vinyl has, in theory, no re-grind in it.
Enjoy,
Rich P