A tiny minecraft mod to get the ore rarity values for botania based on https://gist.github.com/Vazkii/9493322.

mods.toml

modLoader="javafml" #mandatory
loaderVersion="[28,)" #mandatory (28 is current forge version)
[[mods]] #mandatory
modId="worldprofiler" #mandatory
version="${file.jarVersion}" #mandatory
displayName="World Profiler" #mandatory
[[dependencies.worldprofiler]] #optional
    modId="forge" #mandatory
    mandatory=true #mandatory
    versionRange="[28,)" #mandatory
    ordering="NONE"
    side="BOTH"
[[dependencies.worldprofiler]]
    modId="minecraft"
    mandatory=true
    versionRange="[1.14.4]"
    ordering="NONE"
    side="BOTH"

WorldProfiler.java

package com.tome.worldprofiler;

import java.io.File;
import java.io.FileOutputStream;
import java.util.Collection;
import java.util.HashMap;
import java.util.Map;

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;

import com.mojang.brigadier.CommandDispatcher;
import com.mojang.brigadier.context.CommandContext;

import net.minecraft.block.Block;
import net.minecraft.block.BlockState;
import net.minecraft.client.Minecraft;
import net.minecraft.command.CommandSource;
import net.minecraft.command.Commands;
import net.minecraft.tags.BlockTags;
import net.minecraft.util.ResourceLocation;
import net.minecraft.util.math.BlockPos;
import net.minecraft.util.text.StringTextComponent;
import net.minecraftforge.common.MinecraftForge;
import net.minecraftforge.eventbus.api.SubscribeEvent;
import net.minecraftforge.fml.common.Mod;
import net.minecraftforge.fml.event.server.FMLServerStartingEvent;

@Mod(WorldProfiler.MODID)
public class WorldProfiler {
	private static final Logger LOGGER = LogManager.getLogger();
	public static final String MODID = "worldprofiler";

	public WorldProfiler() {
		MinecraftForge.EVENT_BUS.register(this);
	}

	@SubscribeEvent
	public void onServerStarting(FMLServerStartingEvent event) {
		ProfileCommand.register(event.getCommandDispatcher());
	}

	public static class ProfileCommand {

		public static void register(CommandDispatcher<CommandSource> dispatcher) {
			dispatcher.register(Commands.literal("profile_ores")
					.requires(source -> source.hasPermissionLevel(4) && Minecraft.getInstance().isSingleplayer())
					.executes(context -> profile(context)));
		}

		public static int profile(CommandContext<CommandSource> context) {
			try {
				LOGGER.info("Lag incoming!");
				Map<String, Integer> ores = new HashMap<String, Integer>();

				int chunks = 256;
				int range = (int) Math.sqrt(chunks);

				for (int x = 0; x < (16 * range); x++)
					for (int y = 0; y < 128; y++)
						for (int z = 0; z < (16 * range); z++) {
							BlockState state = context.getSource().getWorld().getBlockState(new BlockPos(x, y, z));
							Block block = state.getBlock();
							if (block != null) {
								Collection<ResourceLocation> tags = BlockTags.getCollection().getOwningTags(block);
								for (ResourceLocation tag : tags) {
									String oredict = tag.toString();
									if (oredict.toString().toLowerCase().startsWith("forge:ores/")) {
										int count = ores.containsKey(oredict) ? ores.get(oredict) : 0;
										ores.put(oredict, count + 1);
									}
								}
							}
						}

				String str = "Chunks checked: " + chunks + "\n\n";
				for (String s : ores.keySet())
					str = str + s + " = " + ores.get(s) + " (avg " + ((double) ores.get(s) / (double) chunks)
							+ " per chunk)\n";

				File output = new File("worldprofiler.txt");
				FileOutputStream fiout = new FileOutputStream(output);
				fiout.write(str.getBytes());
				fiout.close();
				context.getSource().sendFeedback(
						new StringTextComponent(String.format("[%s] §aResults saved to %s.", MODID, output.getAbsolutePath())),
						true);
			} catch (Exception e) {
				LOGGER.catching(e);
			}
			return 0;
		}

	}

}