If my calculation is correct (and I always fuck those up) a cubic block with a side of 12 microns would have a volume of around 1.73x10^-15 cubic meters. The density of a neutron star is around 1x10^17 kg/m³ (according to quick google search). This would make the equivalent cube of neutron star “matter” around 173kg which would be slightly heavier than the gold.

However, make the block of pure gold half its size, and as we all know it’s still 110kg.