American Journal of Environmental Sciences 5 (4): 501-507, 2009 ISSN 1553-345X © 2009 Science Publications Corresponding Author: Paola Marini, DITAG-Department of Land, Environment and Geo-Engineering, Politecnico di Torino, Corso Duca Degli Abruzzi 24, 10129 Torino, Italy Tel: 011-0907625 Fax: 011-0907699 501 Rocks with Asbestos: Risk Evaluation by Means of an Abrasion Test Bellopede Rossana, Clerici Carlo, Marini Paola and Zanetti Giovanna DITAG-Department of Land, Environment and Geo-Engineering, Politecnico di Torino, Corso Duca Degli Abruzzi 24, 10129 Torino, Italy Abstract: Naturally occurring asbestos and asbestiform minerals can be found in metamorphic rocks and in the soil of the alluvial plains. Problem statement: The definition of the “free-asbestos rock” and the limit to consider a rock or a soil safe is still a controversial issue. American and European laws did not present any method to define the hazard of the green stones, instead Italian law, in Ministerial Decree1996, established a limit value obtaoined by the determination of the Release Index. In order to detect an asbestos concentration in the rocks, a reliable analytic methodology has been necessary. Approach: An abrasion trial, using the mechanism action of a rotary cylinder, and a Phase Contrast Optical Microscopy (PCOM) method to analyze the powder obtained from the mill, had been used. To simplify PCOM analysis, the sample, recovered from the mill, was selected in particle size classes: large, medium and small. Each class was separated by means of sedimentation in fibrous and granular fractions. Results: The separation of asbestos in large and medium classes was quite good and the fibers had been weighed. For the small class the transformation of visible data into numerical data was complex, but the results had been reliable. Conclusion/Recommendations: The suggested method, although semi-quantitative, could be useful to solve the difficult problem of the analysis of the asbestos content in the rocks or soils. The division into granular classes allowed a more representative sample to be analyzed and better quality slides to be prepared. From the results obtained, the analysis of the small classes by means of PCOM was a critical point: The use of the SEM method can improve it. Key words: Asbestiform minerals, hazard, release index, PCOM INTRODUCTION In mineralogy, the term “asbestiform” is used to describe the specific crystal habit in polyfilamentous fibers organized in bundles, while the term “Asbestos” indicates a group of six minerals (Chrysotile, Tremolite, Actinolite, Antophyllite, Crocidolite and Amosite Table 1) which have the same fibrous crystalline habit and the similar properties like flexibility, high tensile strength, long shape, high mechanical thermal stability, low thermal and electrical conductivity, high absorbency and resistance to acid and bases. Due to these characteristics the asbestos minerals, already used since Romans for their resistance to fire, became from the 19th century very important as industrial minerals [1] . The asbestos bearing lithogies are metamorphosed mafic and ultra mafic rocks and more rarely metamorphosed carbonate rocks, in Fe-cherts and ironstones [2,3] . The asbestos of amphibole is less common than chrysotile, they can be present in the same rocks as serpentine asbestos and all these fibrous minerals may occur in slip-fiber and cross-fiber veins and as mass fiber deposits. Table1: The six industrial asbestos minerals Regulatory Non fibrous Mineral name mineral variety group Formula Chrysotile Antigorite and Serpentine Mg3Si2O5(OH)4 lizardite Crocidolite Riebekite Amphibole Na2(Fe 2+ 3,Fe 3+ 2)Si8O22(OH)2 Tremolite Tremolite Amphibole Ca2(Mg,Fe)5Si8O22(OH)2 Actinolite Actinolite Amphibole Ca2(Mg,Fe 2+ )5Si8O22(OH,F)2 Antophyllite Antophyllite Amphibole (Mg,Fe)7Si8O22(OH)2 Amosite Cummingtonite- Amphibole Mg2 Fe 2+ 5Si8O22(OH)2 Grunerite Many other minerals, such as attapulgite, balangeroite, carlosturanite, erionite, brucite, fluoroedenite, palygorskite, sepiolite, wollanstonite and others can show the asbestiform habit in specifc crystallization conditions, but we can find information on their risk hazard only when, as in the case of Fluoroedenite of Biancavilla (Fig. 1 and 2), an effective link between the presence of the mineral and the increase of mortality has been found [4] . Naturally occurring asbestos and asbestiform minerals can be found also in the soil of the alluvial plain that can be moved and transported far from the place of origin.