Abstract.

The Province of La Rioja has geological features that give it great potential in dimensional stones. Some of these deposits are currently stalled due to problems to get the market. In order to study the effect of geomechanical properties of rocks in their ornamental quality, three sites were selected:

  • Imperial Riojano Red Granite,

  • Black Alcázar Granite

  • Sierra lilac or blue Mara of Sierra de los Quinteros Granite.

To characterize the physical and mechanical properties of these rocks, the following studies were conducted in laboratory: petrographic characterization, physical indexes (dry and saturated density and % absorption), abrasion tests, uniaxial compressive strength in cubic samples and flexural strength on three and four points.

The results obtained shown that the geomechanical properties of lilac and black granites have very good proper for ornamental uses. The test indicates that these rocks are in the range of good quality granites in terms of physical and mechanical properties. The imperial red granite shows a good correlation between the microfracturing and the values obtained from mechanical and physical tests that make a lower quality of this rock. The black granite has very good properties for ornamental purposes, but the levels of jointing at a deposit scale, seriously limit the possibility to produce sized blocks required by the industry. One option to use this stone could be the production of small blocks for tile production but currently there is no market for that in Argentina.

1. Introduction

The exploitation of dimensional stone in Argentina has been determined by quality deposits, type and quality of rocks, access, location, distances to markets and economic policies, mainly those related to the exchange rate.

The Province of La Rioja for decades was recognized for being the main supplier of black granite of Argentina. The rise of the activity took place mainly in times of economic protectionism and high exchange rates prior to the 1980. To the end of this decade and during the 1990's there was a new boom in domestic production of granites which allowed the exploitation of Imperial Red, the Sierra lilac variety and the reopening of old black granite quarries. Because of several reasons related to competition with foreign granites and the complexities of deposits and rocks, black and red granite quarries were paralyzed, just the Blue Mara (ex Lilac) produces intermittently some blocks in the Sierra de los Quinteros.

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