The following subtypes can be distinguished in accordance with their fabric:
Typic. They have an undifferentiated fabric.
Concentric. They have concentric fabric.
Nucleic. They have a distinctive core.
Geodic. They have an interior void.
Septaric. They have a radiating crack pattern.
Pseudomorphic. Their internal fabric is pseudomorphic with another substance.
Halo. They have a strongly impregnative core and a weaker impregnative cortex.
They are also defined by their degree of impregnation (pure, strong, moderate and weak impregnation) and by the sharpness of their boundary (net and diffuse).