Cassiterite

Cassiterite   **This is an online only stone**
Also known as the 'tin stone'
A stone of divinity
Very grounding
Used for deep meditation
Helpful for problem solving, especially in situations involving mathematics 
Increases intellectual abilities in it's wearer
Helps balance the flow of chakra energies, especially the root
Helps ease suffering associated with death
From Namibia
 
These are priced by weight and not necessarily by size.