A grinding machine (20,40) of slab elements which comprises: - a plurality of abrasive tools (24,44) able to come into contact with a surface (T1,T2) of the slab element which transits along an advancing direction; - an optical group (25,45) for each abrasive tool (24,44), wherein each optical group (25,45) is located in proximity of the respective abrasive tool (24,44) and is configured for detecting an image of a contact zone between the surface (T1,T2) and the respective abrasive tool (24,44); and - an electronic control unit operatively connected to each of the optical groups (25,45) characterized in that the electronic control unit is configured for: - determining a physical magnitude of the spark triggered by friction contact between the respective abrasive tool (24, 44) and the slab element based on the image detected by the optical group, said physical magnitude being selected from a group consisting in light intensity of the spark, dimension of the spark, shape of the spark and colour of the spark, - comparing the determined physical magnitude with a predetermined reference (I ref), and - generating an error signal if the physical magnitude differs from the predetermined reference (I ref) of a predetermined significant error; and in that the electronic control unit is also configured for: - determining an amount of material removed by the abrasive tool (24, 44) from the surface (T1, T2) of the slab element based on the image detected by the optical group (25, 45). - a plurality of abrasive tools (24,44) able to come into contact with a surface (T1,T2) of the slab element which transits along an advancing direction; - an optical group (25,45) for each abrasive tool (24,44), wherein each optical group (25,45) is located in proximity of the respective abrasive tool (24,44) and is configured for detecting an image of a contact zone between the surface (T1,T2) and the respective abrasive tool (24,44); and - an electronic control unit operatively connected to each of the optical groups (25,45) characterized in that the electronic control unit is configured for: - determining a physical magnitude of the spark triggered by friction contact between the respective abrasive tool (24, 44) and the slab element based on the image detected by the optical group, said physical magnitude being selected from a group consisting in light intensity of the spark, dimension of the spark, shape of the spark and colour of the spark, - comparing the determined physical magnitude with a predetermined reference (I ref), and - generating an error signal if the physical magnitude differs from the predetermined reference (I ref) of a predetermined significant error; and in that the electronic control unit is also configured for: - determining an amount of material removed by the abrasive tool (24, 44) from the surface (T1, T2) of the slab element based on the image detected by the optical group (25, 45). - determining a physical magnitude of the spark triggered by friction contact between the respective abrasive tool (24, 44) and the slab element based on the image detected by the optical group, said physical magnitude being selected from a group consisting in light intensity of the spark, dimension of the spark, shape of the spark and colour of the spark, - comparing the determined physical magnitude with a predetermined reference (I ref), and - generating an error signal if the physical magnitude differs from the predetermined reference (I ref) of a predetermined significant error; and - determining an amount of material removed by the abrasive tool (24, 44) from the surface (T1, T2) of the slab element based on the image detected by the optical group (25, 45).