Debris
The Debris modification adds realistic destruction elements to the Minecraft world - piles of rubble and bone mounds that can be broken to obtain random items. When these blocks are destroyed, they drop various loot including common building materials (cobblestone, sand, gravel), worn tools (pickaxes and helmets), useful resources (string, clay, redstone, torches, coal) and sometimes more valuable finds (emeralds and diamonds).
Working Mechanism
The item drop system is based on internal loot tables. Piles of rubble and bone mounds use different loot tables, so the set of items from each block type will differ.
Loot tables can be expanded when compatible mods are installed. The current version includes support for Forestry, and future updates plan to add compatibility with other popular modifications.
For pack creators, a feature is planned to integrate external JSON files with loot tables, allowing to add new items to drops or replace existing variants.