Latvian quartz sand from deposits Bale (Devonian period) and Skudras (Jurassic period) was examined. Correlations between the grinding time (4 and 6 hours in the aquatic environment) – dispersion – and grain specific surface area of quartz sand were determined. Specific surface area of grains after grinding significantly increased to 3.19 m2/g, and was more than the specific surface area (0.91 m2/g) of sand power used in the production of concrete. SEM microphotographs of sand ground for 4 and 6 hours showed placoid grains that simulated the quartz crystal structure. The nature and course of development of adsorption and desorption curves of milled quartz sand in practice are the same; hysteresis loop indicates particle crystallinity. The dispersion of sand from both deposits after grinding in water in different modes is the same, i.e., the average grain size after 4 hours of treatment is in the range of 16…19 μ, after 6 hours 12…14 μ. The pozzolanic activity test for the evaluation of ground sand reactivity was carried out. The pozzolanic activity of sand from Bale and Skudras deposits increased with an increase in the specific surface area. The sand of Skudras deposit is characterized by a higher pozzolanic activity. The small increase in reactive CaO in the period from 3 to 14 days shows that the reaction is capable of performing the silica gel layer formed in 3-7 days, and due to agglomeration of gel particles the reaction with alkali in future is limited. The study of morphology and crystalline phases for cement paste with ground Latvian sand during the hydration process has shown that 12…14 μ disperse sand acts as a pore filler and as a pozzolanic additive in cement stimulating the formation of calcium silicate hydrate.