Some astronomers have suggested that cooled white dwarf are made of diamond. Why might it be impractical to mine them?
The surface gravity of a white dwarf is very high, of the order of
A typical white dwarf with mass approximately
The high surface gravity makes it very difficult to escape from the gravitational pull of the white dwarf, even if you were able to collect some material from it - which brings me to the second point...
The material you are attempting to collect from the white dwarf is on average
It's probably easier to make diamonds at home.