Typically, there's an inverse correlation between the quality and quantity of mineral resources. High-grade mineral ores are less common than low-grade ores.
This scarcity of high-grade deposits stems from extensive past mining.
Consequently, remaining deposits are often lower in grade or economically challenging to extract.
The limited availability of superior-quality minerals therefore accounts for this inverse relationship.
The statement and its explanation are both accurate, with the explanation providing a direct justification for the statement.