What's the plural form of porphyre? Here's the word you're looking for.
Answer
The noun porphyre can be countable or uncountable.
In more general, commonly used, contexts, the plural form will also be porphyre.
However, in more specific contexts, the plural form can also be porphyres e.g. in reference to various types of porphyres
or a collection of porphyres.
