Using kalpasi (which is also known as Black Stone Flower) in a biriyani?
Kalpasi is type of lichen, usually used in spices for typical Chettinad and West Indian (Maharashtrian) Cuisines. 

Dry ground kalpasi has little or no smell and should be roasted in little oil to get its actual and full aroma.

It has a distinct smell, which it would impart, if used properly i.e. after roasting (also depends on how and for how much time you marinate).

Its generally used in combination with other spices like cardamom, cloves, bay leaves, cinnamon, nutmeg, star anise, saffron, peppers etc. for flavor. 

On its own, it can't add much flavor.