Cubic feet of granite is mainly used for the detection of parallelism perpendicularity. Main mineral composition of the marble feet to escape the stone, plagioclase, minor olivine, biotite, and trace magnetite, black color, structure, precision codes, after millions of years of aging, even texture, good stability, high strength, hardness high under heavy load to maintain high accuracy. 
 Granite square feet in industrial production and laboratory measurements. Proportion :2970-3070kg / m3. Compressive strength :2500-2600kg / cm3. Elasticity coefficient :1.27-1 .47 × 106N/mm2. Water absorption: 0.13%. Shore hardness: HS70 above. 
 Features and advantages of the granite feet: 
 1, good rigidity, high hardness, wear resistant; 
 Uniform, rock by a long-term natural aging, organizational structure, a very small linear expansion coefficient, internal stress completely disappeared, no deformation, so high precision; 
 3, not afraid of acid, alkaline liquid material erosion, and will not rust, do not need oiling, easy to stick dust, maintenance, easy maintenance, long service life; 
 4, magnetization measurements can move smoothly, Zhise sense, free from damp impact, the plane weighed; 
 5, no scratches, not a constant temperature to prevent temperature measurement accuracy can be maintained at room temperature.