Question

1. the demopolis has been mined since 1900 for use in cement and soil conditioners.
2. is an abundant mineral in alabama that is a major component of sand, gravel, sandstone, and glass manufacturing.

Explanation:

For question 20, Demopolis marl has been mined for cement and soil - conditioners since 1900. For question 21, quartz is an abundant mineral in Alabama used in sand, gravel, sandstone, and glass manufacturing.

Answer:

1. Marl
2. Quartz