Black Tourmaline is grounding and protective. This is one of the crystals that I use in my protection grids.  Great to place by a door for protection.
 
If you want it to stand guard by your door, "plant" it in a pot with soil.
 
1 - Sold
2 - 1" x  1" x .5" - $2.00
3 - 1.25" x .5" x .5" - $2.00
4 - 1.25" x .75" x .25" - $1.00