Edit: Safari was the culprit. Now using Chrome to browse tutorials and haven't had the problem since switching.

Prior text below:
"When playing game in any of the gameplay modes (creative, survival, all the difficulty settings), the mouse cursor will begin to appear over the game. This happens both when the game is full-screen and windowed. Command-Tabbing to another application then back will momentarily remove the cursor, but sometimes only for a second or two. Pressing E to enter the inventory briefly will remove the cursor, but sometimes only for a second or two.

The best solution is to restart the game, which temporarily solves the problem. Often the cursor returns within a few minutes, sometimes in as little as a few seconds."