The modern reading is always shí: 石头 (stone), 宝石 (gem), 钻石 (diamond), 石油 (petroleum), 化石 (fossil). Also a productive radical: 砖 (brick), 破 (break), 磨 (grind).
history
石 has a classical reading dàn used as a dry measure for grain, ten 斗 (about 100 liters), as in 一石粮食 (one dàn of grain). You meet it only in historical texts and old fixed measures. It is also the surname Shí. Modern Chinese keeps shí for the stone meaning and metric units for grain.
Components
pictograph
石shí
stone; rock
Self-component pictograph. Oracle bone forms show a cliff face (厂) with a chunk of stone (口) detached underneath, a rock fallen from the cliff. Itself a Kangxi radical, 石 indexes mineral, masonry, and grinding terms: 矿 (ore), 硬 (hard), 磨 (grind).
Radical
StoneKangxi #112
Highly productive, flags characters about rocks, minerals, masonry, and grinding. Reliable meaning clue: 砂 (sand), 砖 (brick), 砍 (chop), 破 (break), 碎 (shatter), 碗 (bowl), 碰 (bump into), 碑 (stele), 磨 (grind), 矿 (ore). Almost always sits on the left.
