I believe the answer is: Minerals must have a homogeneous chemical composition.
Answer:
cliché
a worn out idea or trite expression
idiom
phrase or expression whose meaning cannot be understood from the ordinary meanings of its words.
category
informal casual speech
Explanation:
<span>What is the anagram for pliers meaning dangers? ... Many words representing items that have an inherent "duality" are treated thus by modern ...</span>
means...you should write a letter to your friend for inviting him/her to join you for a picnic