I am very new to modding and was wondering if I could change what drops when you break a stone block and a gravel block.  I want to have crystals drop from a stone block on a 1% chance and shattered crystal drop from gravel on a 1% chance.

1. Learn about Forge Events.

2. Do NOT proceed until you understand them.

3. Subscribe to HarvestDropsEvent and add new loot to drop list.

 

4. Example:

@SubscribeEvent
public void onHarvestDrops(HarvestDropsEvent event)
{
Block block = event.state.getBlock();
if (block == Blocks.iron_ore)
{
	event.drops.clear(); // you can also clear drops
	event.drops.addAll(some collection of ItemStacks);
}
}

 

To add ItemStack to drop you can simply do: new ItemStack(Item, amount, meta).

Thanks I will definitely take it super slow with all this.  I just wanted to make sure it is doable before I move on with my idea.  This is perfect and exactly what I was looking for.