Implemented original geologist pick logic into the mixin as a starting point. Overwriting the useOn method while creating a unique getMessage alternative method. Also made a separate MineralCacheEntry class as originally it is marked private.

src/main/java/dev/micle/geologistpicktweaks/mixin/IGMineralTestingItemMixin.java

@@ -1,22 +1,145 @@
 package dev.micle.geologistpicktweaks.mixin;
 
+import com.igteam.immersivegeology.common.block.helper.IOreBlock;
+import com.igteam.immersivegeology.common.item.IGGenericItem;
 import com.igteam.immersivegeology.common.item.IGMineralTestingItem;
-import dev.micle.geologistpicktweaks.GeologistPickTweaks;
+import com.igteam.immersivegeology.common.item.helper.IGFlagItem;
+import com.igteam.immersivegeology.core.material.helper.flags.BlockCategoryFlags;
+import com.igteam.immersivegeology.core.material.helper.flags.ItemCategoryFlags;
+import com.igteam.immersivegeology.core.material.helper.material.MaterialInterface;
+import dev.micle.geologistpicktweaks.util.MineralCacheEntry;
+import net.minecraft.core.BlockPos;
+import net.minecraft.network.chat.Component;
+import net.minecraft.tags.TagKey;
 import net.minecraft.world.InteractionResult;
+import net.minecraft.world.entity.player.Player;
+import net.minecraft.world.item.ItemStack;
 import net.minecraft.world.item.context.UseOnContext;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.Level;
+import net.minecraft.world.level.block.Block;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.chunk.ChunkAccess;
+import net.minecraft.world.level.chunk.LevelChunkSection;
+import org.jetbrains.annotations.NotNull;
 import org.spongepowered.asm.mixin.Mixin;
 import org.spongepowered.asm.mixin.Overwrite;
+import org.spongepowered.asm.mixin.Unique;
+
+import java.util.*;
 
 @Mixin(IGMineralTestingItem.class)
-public abstract class IGMineralTestingItemMixin {
+public abstract class IGMineralTestingItemMixin extends IGGenericItem implements IGFlagItem {
+    @Unique
+    public final HashMap<ChunkPos, MineralCacheEntry> geologist_pick_tweaks_1_20_1$mineralCache = new HashMap<>();
+
+    public IGMineralTestingItemMixin(ItemCategoryFlags flag, MaterialInterface<?> material) {
+        super(flag, material);
+    }
+
     /**
      * @author Micle
-     * @reason Improving geologist pick usage logic.
+     * @reason Tweaking geologist pick usage logic.
      */
     @Overwrite
     public InteractionResult useOn(UseOnContext context) {
-        GeologistPickTweaks.LOGGER.debug("HELLO WORLD");
+        Player player = context.getPlayer();
+        ItemStack stack = context.getItemInHand();
+        if (player == null || !stack.getItem().equals(this)) {
+            return InteractionResult.FAIL;
+        }
+
+        Level level = context.getLevel();
+        BlockPos usedPos = context.getClickedPos();
+        ChunkPos centerChunkPos = new ChunkPos(usedPos);
+
+        stack.hurtAndBreak(1, player, (p) -> {});
+
+        MineralCacheEntry cachedEntry = geologist_pick_tweaks_1_20_1$mineralCache.get(centerChunkPos);
+        if (cachedEntry != null) {
+            long currentTimestamp = System.currentTimeMillis();
+            if ((currentTimestamp - cachedEntry.timestamp) > MineralCacheEntry.CACHE_EXPIRY) {
+                geologist_pick_tweaks_1_20_1$mineralCache.clear();
+            } else {
+                player.displayClientMessage(Component.literal(cachedEntry.message), true);
+                return InteractionResult.SUCCESS;
+            }
+        }
+
+        int centerChunkX = centerChunkPos.x;
+        int centerChunkZ = centerChunkPos.z;
+        int minBuildHeight = level.getMinBuildHeight();
+        int maxBuildHeight = level.getMaxBuildHeight();
+        int sectionMin = level.getSectionIndex(minBuildHeight);
+        int sectionMax = level.getSectionIndex(maxBuildHeight);
+
+        Set<MaterialInterface<?>> oreSet = new HashSet<>();
+        TagKey<Block> allOresTag = BlockCategoryFlags.ORE_BLOCK.getCategoryTag();
+        chunkScan: for (int dx = -1; dx <= 1; dx++) {
+            for (int dz = -1; dz <= 1; dz++) {
+                ChunkAccess chunk = level.getChunk(centerChunkX + dx, centerChunkZ + dz);
+
+                for (int sectionIndex = sectionMin; sectionIndex < sectionMax; sectionIndex++) {
+                    LevelChunkSection section = chunk.getSection(sectionIndex);
+
+                    if (section.hasOnlyAir()) {
+                        continue;
+                    }
+
+                    if (!section.maybeHas(b -> b.is(allOresTag))) {
+                        continue;
+                    }
+
+                    for (int x = 0; x < 16; x++) {
+                        for (int y = 0; y < 16; y++) {
+                            for (int z = 0; z < 16; z++) {
+                                BlockState blockState = section.getBlockState(x, y, z);
+                                if (blockState.is(allOresTag)) {
+                                    IOreBlock ore = (IOreBlock) blockState.getBlock();
+                                    oreSet.add(ore.getOreMaterial());
+                                    if (oreSet.size() >= 3) {
+                                        break chunkScan;
+                                    }
+                                }
+                            }
+                        }
+                    }
+                }
+            }
+        }
+
+        Component message = geologist_pick_tweaks_1_20_1$getMessage(oreSet);
+
+        player.displayClientMessage(message, true);
+        geologist_pick_tweaks_1_20_1$mineralCache.put(centerChunkPos, cachedEntry);
 
         return InteractionResult.SUCCESS;
     }
+
+    @Unique
+    private static @NotNull Component geologist_pick_tweaks_1_20_1$getMessage(Set<MaterialInterface<?>> oreSet) {
+        Component message;
+        if (oreSet.isEmpty()) {
+            message = Component.translatable("immersivegeology.prospecting_pick.nothing");
+        } else {
+            List<MaterialInterface<?>> found = new ArrayList<>(oreSet);
+            String messageKey = "immersivegeology.prospecting_pick.found";
+            String materialsText;
+
+            switch (found.size()) {
+                case 1:
+                    materialsText = "Found Traces of " + found.get(0);
+                    break;
+                case 2:
+                    materialsText = "Found Traces of " + found.get(0) + " and " + found.get(1);
+                    break;
+                default: // 3 or more
+                    materialsText = "Found Cluster of " + found.get(0) + ", " + found.get(1) + " and " + found.get(2);
+                    break;
+            }
+
+            message = Component.translatable(messageKey, materialsText);
+        }
+        return message;
+    }
 }

src/main/java/dev/micle/geologistpicktweaks/util/MineralCacheEntry.java

@@ -0,0 +1,15 @@
+package dev.micle.geologistpicktweaks.util;
+
+/**
+ * @author muddykat
+ */
+public class MineralCacheEntry {
+    public static final long CACHE_EXPIRY = 10 * 1000;
+    public final String message;
+    public final long timestamp;
+
+    public MineralCacheEntry(String message) {
+        this.message = message;
+        this.timestamp = System.currentTimeMillis();
+    }
+}