Obsidian is the toughest material in Minecraft. It is formed when water meets lava. If you try to mine Obsidian, with anything other than a diamond pickaxe, you will fail. Usually, there is lava right underneath the obsidian that you want to mine, and as soon as you do it will just burn up, but if you follow my instructions you will have a stockpile of the material in no time.
First you must find the right spot to mine the obsidian. Look for an area that still has flowing water, and is not just surrounded by stagnant water. Find the edge of the Obsidian that is closest to a safe location. Avoiding lava is a must when mining this material. Make a barricade around yourself by using stone if you are being pushed around by running water. Make sure that you are using a diamond pickaxe, because as stated before, no other pickaxe will do for this job.
Once you start mining, you will notice that it takes a very long time to mine. This is normal, just be patient. The first obsidian block that you mine might be burned by the lava underneath, but this is a minor loss. The water should turn the lava that just burned your obsidian into the same. This is the one that you want to go after. Get as close as you can to the obsidian, but not so close that you will fall into the hole once you mine it. Once you pick away at it long enough, it should just fly into your pocket.
Another method for people who are higher level would be to go to “The End”, where there are giant pillars of obsidian that are very easy to mine. Also, if you want to speed up the amount of time it takes to mine the material, enchanting your diamond pickaxe with “Efficiency” will make things thirty percent faster.
You can use your newly mined obsidian to do many things, including; making a portal to the “Nether”, crafting enchantment tables, ender chests, and beacon blocks. So, if you intend to ever enchant an item, you are going to have to put up with mining a few, slow, blocks of obsidian, but it is worth it in the end. One last tip would be to find a small lava pond, fill a metal bucket with water, and then pour it onto the lava pond, turning it all into minable obsidian.