Fill the beaker halfway with water. Note the level of the water.
Put the mineral into the beaker. Make sure it fully submerges in the water.
Note the level of the water once again.
Calculate the difference in the amount of water before the mineral was put in and after it was put in.
Spill out the water from the beaker.
Weigh the empty beaker.
Fill the beaker with the amount of water the mineral displaced (calculated in Step 4).
Weigh the beaker with the water.
Subtract the weight of the empty beaker from the weight of the beaker calculated in Step 8. This is the weight of the water displaced by the mineral. Accordingly, it has the same volume as the mineral.
Weigh the mineral.
Divide the weight of the mineral by the weight of the water it displaced. This will be the specific gravity of the mineral.