Sample r is highly desired in the energy industry because it is the most "clean" variety. using your knowledge of metamorphic processes, how do you think this rock becomes so "clean" compared to its protolith?

the rock is anthracite and it's protolith is coal

Bituminous Coal permits more contaminants noticeable all around and isn't as naturally well disposed as Anthracite coal.

Explanation:

The stone anthracite is so perfect due to it high review of coal. It creates less smoke when consuming and furthermore long-lasting consuming. It's utilized in the vitality business on the grounds that having a high vitality thickness of 33 MJ/kg and over 86% of carbon.  

Anthracite coal is a profoundly carbonated petroleum product that creates the most elevated warmth out of every single non-renewable energy source, and the low sulfur content in Anthracite makes it a significantly more spotless consuming.

Moreover, Anthracite coal creates no smoke or particulate emanations and isn't a fire danger source when utilized in more flowed aviation routes like stacks or channels.