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rock dust. Both dusts were applied using the standard spray application methods and results showed that the conventional rock dust absorbed moisture from the mine wall and was not dispersible within a fairly short time period. The new Imerys rock dust proved to be more moisture tolerant and has remained dis- persible for more than six months. The new moisture-tolerant product looks, feels and can be applied just like oth- er conventional North American rock dusts. In fact, it is greater than 99% of the same makeup as the original Imerys rock dust; therefore the product can easily be integrat- ed into current dry dusting methods. In examination of the new product, it was not- ed that due to the moisture tolerance, it could potentially flow smoother and further down trickle dusting systems in addition to not clogging sprayers. This could potential- ly mean less maintenance issues. Unlike commonly used limestone, mar- ble-based rock dusts have some additional features that make the new moisture-toler- ant dust more appealing. Mined from the world's largest open-pit marble quarries, Imerys' marble-based material has high brightness and whiteness, providing great contrast against coal dust. With the new hydrophobic product, this visual contrast should be higher since the product doesn't cake and turn into gray mush. This means that when you inspect your walls, you can clearly see where the moisture-tolerant product still exists and where the coal dust has settled on top. Expected Market Impact The new moisture-tolerant product pro- vides a ready-to-use "fix" material for the North American market to address the caking issues in high-moisture and wet coal mine environments. Internationally, moisture-tolerant products do exist in other countries in Europe and the U.K. However, their dusts are designed for use in bulk dust systems where it is stored for long periods of time in bag or trough deployment systems. Being designed in North America, the uniqueness of Imerys' new moisture-tolerant rock dust is that it is meant to be applied the same way as other North American rock dusts, using the same equipment. This means that North American operators do not need to invest in new equipment or learn any new application methods in order to use the new moisture tolerant product. Imerys also expects the new moisture- tolerant rock dust to help mine operators save on their overall cost of ownership. With its long-lasting properties, the cost of reap- plication is expected to be reduced, there- fore reducing the amount of material and labor for this ongoing process. The initial cost-savings evaluation focuses on the non- active sections of the mines where a long- lasting material could reduce the reapplication maintenance to once daily, weekly, or even less depending on the amount of float coal dust present in the area. The idea is that with the improved moisture tolerance, the main focus of com- pliance will be on the coal dust parameters, o p e r a t i n g i d e a s c o n t i n u e d 54 www.coalage.com July 2015 T able 2 — Imerys Rock Dust Samples Comparison to 30 CFR 75.2 Traditional rock dusts cake when they dry.