Mark of the Elemental (Earth)

You have manifested the mark of the Earth Elemental. Determine its appearance. You gain the following benefits:

• You can burrow up to 30 feet through nonmagical, unworked earth and stone. While doing so you do not disturb the material you move through. You cannot end your turn inside earth or stone 
• You can cast the spell stoneskin once per long rest. This spell does not use a spell slot.
• You can speak Terran.