Balmer is the lava-flooded remains of a lunar impact crater. Only the heavily worn southern and eastern sections of the crater still survive; the remainder being overlaid by a lava flow that joins to the nearby mare. Balmer lies to the east-southeast of the crater Vendelinus.
Balmer was considered a Constellation Region of Interest. Light plains deposits overly mare basalt, as evidenced by multiple dark-halo craters.
By convention these features are identified on lunar maps by placing the letter on the side of the crater midpoint that is closest to Balmer.