Sillimanite with an incredibly well-defined cat's eye.
 The line of light seems to slide across the surface of the gem depending on the direction of the light source.
 This phenomenon called chastisement is produced by microscopic parallel inclusions that reflect light through the size of the cabochon.
 
 weight: 4.87ct
 hardness: 6.5-7.5
 origin: India
 color: gray with chatôyance
 crystal system: orthorhombic
 dimensions: 10.6x5mm