Typical volcanic rocks such as tuffs and basalts, commonly found throughout Armenia, were used for millennia as building materials for architectural monuments and are now used for mass construction. The author used this information to link the study of these stones' properties and structure with their actual durability as part of buildings, and to establish generally valid relationships. For example, several varieties of highly porous tuffs of relatively low resistance were found to be more durable than some denser and more highly resistant tuffs. The author tried to elucidate the causes of this phenomenon. -- AATA