Rock texture is of great importance in understanding the mechanical properties of a rock. Los Angeles and studded tyre tests were used to assess the mechanical properties of homogeneous acidic plutonic and volcanic rocks and these properties were related to the rock texture using image analysis and the more common optical microscopy. The image-analysing technique was based on SEM/ BSE images, where the perimeter was measured on each mineral phase in order to numerically quantify a texture parameter. The results demonstrate that rocks with high perimeter values have the best resistance to fragmentation and abrasion. A high perimeter corresponds to ®ne-grained rocks where the minerals occur as individual grains rather than monomineralic aggregates. An increase in grain size and the formation of mineral aggregates of the same phase have a negative effect on the quality of the rock.Re Âsume  La texture d'une roche joue un ro Ãle important dans son comportement me Âcanique. L'essai Los Angeles et l'essai avec pneus cloute Âs ont e Âte  utilise Âs pour e Âvaluer les caracte Âristiques me Âca niques de roches plutoniques et volcaniques acides homoge Ánes. Ces caracte Âristiques ont e Âte  rapproche Âes d'une description de la texture base Âe sur le microscope optique. L'analyse d'image a porte  sur les images obtenues au microscope e Âlectronique a Á balayage en e Âlectrons re Âtrodiffuse Âs, ou Á les pe Ârime Átres de chaque phase mine Ârale ont e Âte  mesure Âs a®n d'obtenir un parame Átre nume Ârique relatif a Á la texture de la roche. Les re Âsultats obtenus montrent que les roches pour lesquelles ce parame Átre a une forte valeur pre Âsentent les meilleures re Âsistances a Á la fragmentation et a Á l'abrasion. Un pe Ârime Átre e Âleve  correspond a Á des roches a Á grain ®n ou Á les mine Âraux se pre Âsen-tent en grains individuels pluto Ãt qu'en agre Âgats monomine Âraux. Une augmentation de la taille des grains et la formation d'agre Âgats mine Âraux d'une me Ãme phase mine Ârale ont un effet ne Âgatif sur la qualite  de la roche.

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Cited documents indicate that industrial production of building stones of the Hallandia gneiss from SW Sweden (Halland County) goes back to at least the 1850s when large quantities of paving stones were exported to Germany and Denmark. It is most likely that quarry operations have been going on for a much longer period, mostly for local needs.The Hallandia gneiss is an aesthetically distinct gneiss unit characterized by multiple phases of deformation and veining at high-grade metamorphic conditions, unique with few, if any, equivalents in the world. Remnants of about 500 quarries (including small examples) have been documented in the area. The occurrence of Hallandia gneiss is limited to the coastal areas of SW Sweden where there are strong demands on the land for recreation and cultural heritage. The unique and restricted occurrence of the Hallandia gneiss to an area with strong competing interests of land use has resulted in severe concerns about the supply of this building stone material.The need to safeguard a future supply of this rare stone type is urgent. This paper provides an outline of its unique geology, historic and present use, along with its technical and aesthetical properties.

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