A new quality factor for the building stone industry: a case study of stone blocks,slabs, and tiles

In building stones, discontinuities, non-uniformity, and irregular shape are among the problems that reduce the quality of products. Stone blocks, slabs, and tiles are the main products of quarries and stone processing plants. Quantifying the quality is a key factor in valuation of these products. This paper proposes a quality factor formula to determine the quality of stone blocks (three-dimensional) and products from stone processing plants (two-dimensional). This factor, which shows the uniformity and esthetic index of a piece of stone, is determined based on the shape quality (α), number, size, and esthetic quality (β) of the pieces and the discontinuity factor (γ) that separates the pieces. The quality factor is defined in a way that each previously mentioned characteristic of a piece is involved in the quality factor formula calculation. The quality factor ranges between 0 and 1 and can be expressed as a percentage. The proposed quality factor was calculated for a number of different stone blocks, slabs, and tiles to examine the validity of the quality factor formula. The results showed that the shape quality is the most significant parameter in determining the quality of stone blocks in quarries. Moreover, in processing plant products the esthetic quality and the number of stone pieces in a product are the key factors for determination of their quality. The discontinuity factor is a parameter that reduces the quality of stone products significantly. Furthermore, the quality factor formula can be used as a convenient tool for classifying the products of quarries and stone processing plants.