Question

insert one comma to separate the coordinate adjectives.
volcanic ash, which has an abrasive sandy texture, can include various identifiable particles: crystals, minerals, bits of pumice, shards of volcanic glass, and miscellaneous rock fragments.

Explanation:

Coordinate adjectives are adjectives that modify the same noun and can be separated by a comma. In the phrase "abrasive sandy texture", "abrasive" and "sandy" are coordinate adjectives as they both describe the texture.

Answer:

Volcanic ash, which has an abrasive, sandy texture, can include various identifiable particles: crystals, minerals, bits of pumice, shards of volcanic glass, and miscellaneous rock fragments.