Obsidian is one of the toughest blocks that can be mined in survival Minecraft. When lava comes in contact with water, it turns into an obsidian block. To mine an obsidian block, players need a diamond or netherite pickaxe. It also has the highest breaking time in Minecraft. https://www.sportskeeda.com/minecraft/top-5-uses-obsidian-minecraft
According to Fandom Minecraft Wiki https://minecraft-archive.fandom.com/wiki/Obsidian, It takes 250 seconds to break an obsidian block by hand, and 21.85-125 seconds to break it with a pickaxe weaker than diamond or netherite, although neither will yield any obsidian.