I like your use of camera angles, and the small amount of animation that's there works well enough to tell the story. However, this is still a little short. I would suggest creating more suspense by adding a few more shots of the character mining the diamond block. Perhaps the look on his face could suggest that he's hungrily waiting for the diamonds to pop out, which will make his "FFFFFUUUUUUUUUUUUUU--" more justified and believable to the audience. Besides, I'm pretty sure diamond takes longer to mine with a stone pickaxe. Also, some non-Minecraft players might not understand that the stone pickaxe was the cause of this, so maybe a second scene could be added, where the player finds another diamond vain, mines it with his iron pickaxe, and the diamond falls into the lava. Just a suggestion.
All in all, this is pretty decent for your first animation. Keep practicing!