After some googling, some of the heavier rock types are 3g/cm^3, which is 3000kg/m^3
If we use the person as a rough ruler of 1.6m, the rock is about 5 person wide, and 3 person high (eye measure), give or take. And if we say it’s 3 person deep, then it has a rough mass of 5331.63000 = 216 000 kg, which is in the same order of magnitude.
Close enough to check out, I’d say.
Edit: I realized since the actual ruler we use is 1.6m (assumed), it should be multiplied by 1.6 three times (one for each dimension/length), not just once. If we do that, we end up with 921 600 kg instead, putting 500 000 kg well within the range of possibilities from a quick calculation.
Edit 2: as pointed out below, the actual correct estimation would be 553 tons