In this paper are presented the relationships found between first geotechnical results and geologic and petrography characteristics studied in aggregates of Buenos Aires province (Argentina). Samples are coming from main aggregates quarries of Sierras Septentrionales near Olavarría and Tandil city. The observations indicate that geotechnical results are not only dependent on the mineralogy of the rock, but also it performs supreme importance its texture, which is directly linked by the geological origin. On the other hand is estimated that crushing technology used at cracking plants must be adapted to the characteristics mentioned of the rock to promote their properties and to obtained aggregates which expire with the needs of the market.