A grinding machine of slab elements (T) which comprises: - a plurality of abrasive tools able to come into contact with a surface (T1,T2) of the slab element (T) which transits along an advancing direction (A); - an optical group for each abrasive tool , wherein each optical group is located in proximity of the respective abrasive tool and is configured for detecting an image (I2) of a contact zone between the surface (T1,T2) and the respective abrasive tool ; and - an electronic control unit operatively connected to each of the optical groups 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 and the slab element (T) based on the image (I2) 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 from the surface (T1, T2) of the slab element (T) based on the image detected by the optical group . - a plurality of abrasive tools able to come into contact with a surface (T1,T2) of the slab element (T) which transits along an advancing direction (A); - an optical group for each abrasive tool , wherein each optical group is located in proximity of the respective abrasive tool and is configured for detecting an image (I2) of a contact zone between the surface (T1,T2) and the respective abrasive tool ; and - an electronic control unit operatively connected to each of the optical groups 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 and the slab element (T) based on the image (I2) 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 from the surface (T1, T2) of the slab element (T) based on the image detected by the optical group . - determining a physical magnitude of the spark triggered by friction contact between the respective abrasive tool and the slab element (T) based on the image (I2) 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 from the surface (T1, T2) of the slab element (T) based on the image detected by the optical group . <EOS>