The Executive Director of Sustainability and Institutional Relations, Luiz Eduardo Osorio, participated on June 7 in the launch of the Vale Quartz Project, an initiative that uses quartz (silica) sand in iron ore mining tailings to replace natural quartz in the production of quartz surfaces, engineered stone products that are an alternative to marble and granite. The event was held in Saint-Prex, Vale’s headquarters in Switzerland.
The project was developed by Vale Switzerland employee, Emile Scheepers, and focuses on creating an ecosystem that aims to transform iron ore tailings into a recycled sand, currently piloting with the quartz surface industry to supply a sustainable alternative to natural quartz in the production of durable and beautiful countertops. The pilot may also become a blueprint for supplying recycled sand to other industries, such as industries that produce concrete products (eg railway sleepers), uses plaster sand (eg for brick laying) and perhaps even in the sports field, on golf courses and beach volleyball courts.
Engineered stone is an alternative to natural stone, like granite or marble. The manufacturing process begins with selection of raw quartz materials. They are crushed and blended in the ratio of 93 % quartz, 7% polyester resin, colour pigments and selected aesthetic additives, with the recipes varying depending on desired colour and aesthetic properties. The mixture is compacted into slabs by a vacuum and vibration process of approximately 100 seconds at a pressure of about 100 t. This process minimises porosity and reduces water absorption. The slabs are then cured in a kiln at a temperature of 85 degrees for a period of 30 minutes to attain the essential properties of resistance to stain and impact.
From the start of the project, Vale has been working closely with leaders in the engineering stone manufacturing industry to develop recipes using quartz-rich tailings as a substitute for primary quartz in the countertops. When in 2014 the first consignment of Vale tailings (SiO2 76% & Fe 16%) were dispatched, pilot scale production got underway that would create what would become the first engineering stone samples of its kind in the world. More innovative engineering stone samples followed, with the introduction of veins in the design. But these early samples were mostly dark in colour, with the 16% Fe content the main reason. This left limited options with regards to the choosing a colour of any future final product.
Through Vale’s continued technological efforts to reduce iron content in its tailings, the fortuitous result has been that the subsequent tailings product has continued to increase its quartz content (becoming whiter) and with it the colour control Vale’s silica-rich tailings can demand in the industry. So when in 2017 another consignment of Vale tailings were dispatched for testing, the SiO2 content was higher than 90% and the Fe content lower than 7%.