Extreme Hills

Extreme Hills is a hilly biome and isn't too rare. This is the only biome in which emerald ore spawns. With its mountains, you can build a bridge from one mountain to another. Fun? This biome is common near a taiga biome. This is because they are both cold biomes. In cold biomes, it snows above y=95.

Extreme Hills+ is a variation where spruce trees spawn. These biomes usually reach higher levels than the normal extreme hills biome.

Extreme Hills M consists of huge gravel mountains which can reach over y=135. Dirt and grass paths are sometimes found in this biome.

Extreme Hills+ M conbines extreme hills+ and extreme hills M by having more of a mixture of grass and gravel.

Extreme Hills Edge is a biome not currently used in Minecraft. You can still get it on the customized world type.