Worth $24
Spawn Chance Spawns everywhere (not including ores) at -777.
Best Way to Obtain

Dig all the way under Granite's level ending.

Obsidian is the fourth layer of the mine, packed down beneath granite, dirt, and stone. It is found between -777 and -1,602. Obsidian sells for $24, and it is completely black and hard. To be able to see clearly at obsidian depth, players are recommended to upgrade Visibility. To mine in the obsidian layer, the player must have 10,000 total mined blocks. Tektite has a habit of blending in with it at times, but players will still be able to distinguish its red glow If they are not digging straight down.

Obsidian takes a long time to mine, and a lot of money to upgrade to mine obsidian faster. Because of this, when mining, players tend to mine in granite, unless they have insta-mine, sandbox, or maxed their obsidian upgrades. However, it is the one of the only layers that contains unobtainium to spawn in it (unobtainium can be found in layers below obsidian) (it can also spawn in granite, but is UNIMAGINABLY rare in granite). Fire Crystal is more commonly found in obsidian, although still really rare.

Silver, Gold, Obsidian, Ruby, Sapphire, Emerald, Diamond, Uranium, Turquoise, Amethyst, Platinum, Tektite, Adurite, Fire Crystal, and Unobtainium can be found at this layer. Every single rare except Viridian can be found in this layer. Also, they're more likely to be found in Obsidian, because Obsidian is the deepest layer. You are most likely to find Uranium by digging straight down or by using Nuke, the purple dynamite.

This is known for being a very valuable layer. You will often see experienced players selling enough obsidian to have a message appear ("Player X has sold Obsidian for Y amount of money."), so getting lots of this can be good.