Kshtigarbha Bodhisattva, known as Jizō in Japan, is usually depicted as a monk, carrying a staff and a "wish-fulfilling jewel". Kshtigarbha's name translates as "earth store" or "earth treasury".
Kshtigarbha symbolises gentleness and the importance of offering. It is traditional to make offerings of stones to Kshtigarbha, and when we truly give ourselves to practice, we find that this "stone" we have offered, which we may have thought of as just an ordinary pebble, is in fact a precious stone. It is the gem of the "true wish already fulfilled".
From the Shasta Abbey website:
Kshtigarbha (C: Ti-ts’ang; J: Jizo) “He Who is the Earth’s Treasure House.” The embodiment of benevolence and kindness and a special protector of children, animals, travelers and pregnant women. Having taken a vow to live in the hells until all are free of them, he holds a staff with which to force open the gates of the hells we are putting ourselves through, and a radiant jewel with which to dispel the darkness of delusion within.