We are all familiar with how a coffee bean typically consists of two seeds, with their flat sides facing towards each other. However, there are certain times that these beans mutate and a peaberry is born.
Its formation occurs when only one of the usually two ovules fails to pollinate. This means only one bean gets to live inside the cherry developing a small, rounded shape that's much denser than the regular beans.
There is no way to identify a peaberry before it's removed from the cherry. In addition, they compose about 5% of the total coffees harvested. They're pretty common in Arabica and Robusta varietals, and in regions like Tanzania, Kenya, and Hawaii.