What is the difference ferromagnesian and non-ferromagnesian minerals?

Ferromagnesian                   vs.            non-ferromagnesian
                      
1-Contains Magnesium and Iron          1- Contains little or no Magnesium &
as major components                               Iron

2- Color: very  dark                               2- Color: Generally lighter

3- Density relatively high                      3- Density relatively low

Answerglycogen;