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.
 
7 - 3" x 1" x .5" - $3.50
8 - 2" x  1" x 1" - $3.00
9 - 2.5" x 1" x .75" - $3.00
10 - 1.5" x 1" x .5" - $2.00
11 - 1.5" x 1" x .75" - $3.00
12 - 1.75" x 1" x .5" - $3.00