Other forms: shards
If you break a mirror, the thin sharp pieces you want to avoid are shards. A shard is simply a broken piece of metal, glass, stone, or pottery with sharp edges.
Don't confuse shard with shred, meaning to cut into strips, or chard, a leafy green vegetable. You could use a shard of metal to shred chard into salad, but be careful that you don't cut your hands to shreds!