Find amethyst geodes underground
Look for calcite blocks surrounding the smooth basalt layer in the geode
Mine calcite with any pickaxe
Use a pickaxe enchanted with Silk Touch to collect the block itself
Break the calcite block to obtain calcite as an item
Search deepslate and stone caves near Y-level 0 to 70 for geodes
Use the Creative inventory in Creative mode to get calcite instantly
Use the `/give` command in Java or Bedrock Edition if cheats are enabled