M515 - Czech Republic

Called Hermanov Spheres after the location where these unusual specimens are collected in Hermanov, Czech Republic.
 

Hardness 2-1/2 to 3.  

Basic potassium, magnesium, iron, aluminum silicate; mica group.
 
Biotite is a common accessory mineralin plutonic, volcanic, and certain metamorphic rocks.  (Schist and gneiss.)