Sulfur in Quartz from South Africa. Approximately 1 inch.

The fun part of Sulfur in Quartz is that when struck together it produces the smell of rotting eggs. They are a great converastion piece and is best to have them in pairs so you can demostrate the smell part.
Energetically, Sulfur in Quartz, increases energy and motivation, amplifies the desire to create your own path and achieving your goals.