diff --git a/src/main/java/dev/draylar/magna/mixin/AbstractBlockStateMixin.java b/src/main/java/dev/draylar/magna/mixin/AbstractBlockStateMixin.java
new file mode 100644
index 0000000..9fd5e81
--- /dev/null
+++ b/src/main/java/dev/draylar/magna/mixin/AbstractBlockStateMixin.java
@@ -0,0 +1,62 @@
+package dev.draylar.magna.mixin;
+
+import dev.draylar.magna.api.MagnaTool;
+import net.minecraft.block.AbstractBlock;
+import net.minecraft.block.BlockState;
+import net.minecraft.entity.player.PlayerEntity;
+import net.minecraft.item.ItemStack;
+import net.minecraft.util.math.BlockPos;
+import net.minecraft.world.BlockView;
+import net.minecraft.world.World;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.Unique;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Inject;
+import org.spongepowered.asm.mixin.injection.callback.CallbackInfoReturnable;
+
+import java.util.List;
+
+/**
+ * A mixin that calculates the block breaking delta for {@link MagnaTool MagnaTool}s.
+ */
+@Mixin(AbstractBlock.AbstractBlockState.class)
+public class AbstractBlockStateMixin {
+    /**
+     * Compute the block breaking delta for {@link MagnaTool}s. If the held item is not a MagnaTool, this mixin
+     * does nothing.
+     *
+     * <p>The delta is computed by taking the minimum delta of the affected blocks. Mining speed is effectively limited
+     * by the hardest block being broken.
+     */
+    @Inject(
+            method = "calcBlockBreakingDelta",
+            at = @At("HEAD"),
+            cancellable = true
+    )
+    public void calcBlockBreakingDelta(PlayerEntity player, BlockView world, BlockPos pos, CallbackInfoReturnable<Float> cir) {
+        ItemStack stack = player.getInventory().getMainHandStack();
+        if (stack.getItem() instanceof MagnaTool tool) {
+            cir.cancel();
+            int radius = tool.getRadius(stack);
+            cir.setReturnValue(calculateDelta(tool, player, radius));
+        }
+    }
+
+    @Unique
+    private static float calculateDelta(final MagnaTool tool, final PlayerEntity player, final int radius) {
+        World world = player.getWorld();
+
+        // Even though we already have the BlockPosition that the player is targeting, the side information wasn't
+        // passed along, which is necessary for figuring out how to expand the radius. Just throw that away and
+        // recompute.
+        List<BlockPos> blocks = tool.getBlockFinder().findPositions(world, player, radius);
+
+        return blocks.stream()
+                .map(pos -> {
+                    BlockState state = world.getBlockState(pos);
+                    //noinspection deprecation
+                    return state.getBlock().calcBlockBreakingDelta(state, player, world, pos);
+                })
+                .min(Float::compare).orElseThrow();
+    }
+}
diff --git a/src/main/resources/magna.mixins.json b/src/main/resources/magna.mixins.json
index 833c6a8..be088b4 100644
--- a/src/main/resources/magna.mixins.json
+++ b/src/main/resources/magna.mixins.json
@@ -3,6 +3,7 @@
   "package": "dev.draylar.magna.mixin",
   "compatibilityLevel": "JAVA_8",
   "mixins": [
+    "AbstractBlockStateMixin",
     "BlockMixin",
     "PlayerInventoryMixin",
     "ServerPlayerInteractionManagerMixin",
diff --git a/src/testmod/java/dev/draylar/magna/test/MagnaTest.java b/src/testmod/java/dev/draylar/magna/test/MagnaTest.java
index b190af5..286a582 100644
--- a/src/testmod/java/dev/draylar/magna/test/MagnaTest.java
+++ b/src/testmod/java/dev/draylar/magna/test/MagnaTest.java
@@ -4,6 +4,7 @@
 import dev.draylar.magna.item.ExcavatorItem;
 import dev.draylar.magna.item.HammerItem;
 import net.fabricmc.api.ModInitializer;
+import net.minecraft.block.BlockState;
 import net.minecraft.entity.player.PlayerEntity;
 import net.minecraft.item.Item;
 import net.minecraft.item.ItemStack;
@@ -31,6 +32,18 @@ public void onInitialize() {
                 new HammerItem(ToolMaterials.DIAMOND, 0, 0, new Item.Settings())
         );
 
+        // Standard hammer with a particularly slow mining speed. Useful for testing break speed.
+        Registry.register(
+                Registries.ITEM,
+                new Identifier("magna", "hammer_slow_test"),
+                new HammerItem(ToolMaterials.DIAMOND, 0, 0, new Item.Settings()) {
+                    @Override
+                    public float getMiningSpeedMultiplier(ItemStack stack, BlockState state) {
+                        return 1.0f;
+                    }
+                }
+        );
+
         // Standard Hammer with a tool material of Diamond and a modified depth.
         Registry.register(
                 Registries.ITEM,