I have never heard of Black Topaz, though having done quite a lot of
work with people in the metaphysics you might actually be looking for
Black Tourmaline also called Schorl. This stone is both a healing
stone and protector from negative energy.
For a good luck/healing stone I would normally suggest green
Jade/Jadeite as it is used extensively in China and many other
Oriental countries. Jadeite is usually of course preferred but
budgets often mean using B.C. Jade also known as Nephrite Jade.
Hope this helps