Reference Mission Lunar Sample Return Mass

In the original reference mission, 200 lbs (95 kg) lunar rock samples were to be returned. However, that was based on using hypergolic propellants with an Isp of about 260 or so. If a higher-performance cryogenic system is to be used, then that 200 lbs would increase substantially, to 500 lbs or more.

For comparison here are masses of geologic samples (bulk regolith, rocks, and cores) brought back on various Apollo missions.

Apollo 11: 47.6 lbs (21.6 kg)
Apollo 12: 75.6 lbs (34.3 kg)
Apollo 14: 93.3 lbs (42.3 kg)
Apollo 15: 170.4 lbs (77.3 kg)
Apollo 16: 211.0 lbs (95.7 kg)
Apollo 17: 243.7 lbs (110.5 kg)

Total all missions: 841.6 lbs (381.7 kg) given 2196 sample numbers and cut into 80,000 pieces (as of 1992)

Source:
Wilhelms, D.E, 1993. To a Rocky Moon. Univ. Arizona Press, Tucson.
Heiken et al, 1991. Lunar Sourcebook: A User's Guide to the Moon. Cambridge University Press, Cambridge.