The density of pyrite is 5.02 g/ml. This means that for every milliliter of pyrite, there are 5.02 grams of pyrite. Therefore, a piece of pyrite with a volume of 10 ml will have a mass of:

```

mass = density × volume

mass = 5.02 g/ml × 10 ml

mass = 50.2 g

```

Therefore, the mass of a piece pyrite that has volume 10 ml is 50.2 g.