Grinding Test on Tremolite with Fibrous and Prismatic Habit

Abstract

The main objective of this work is the evaluation of the morphology change in tremolite particles before and after a grinding process. The crushing action simulates anthropic alteration of the rock, such as excavation in rocks containing tremolite during a tunneling operation. The crystallization habit of these amphibolic minerals can exert hazardous effects on humans. The investigated amphibolic minerals are four tremolite samples, from the Piedmont and Aosta Valley regions, with different crystallization habits. The habits can be described as asbestiform (fibrous) for longer and thinner fibers and non-asbestiform (prismatic) for prismatic fragments, also known as “cleavage” fragments. In order to identify the morphological variation before and after the grinding, both a phase contrast optical microscope (PCOM) and a scanning electron microscope (SEM) were used. The identification procedure for fibrous and prismatic elements is related to a dimensional parameter (length−diameter ratio) defined by the Health and Safety Executive. The results highlight how mineral comminution leads to a rise of prismatic fragments and, therefore, to a potentially safer situation for worker and inhabitants.

Keywords

• tremolite
• Naturally Occurring Asbestos (NOA)
• asbestos
• grinding test
• PCOM
• image analysis