مِن عَيْنٍ

مِن عَيْنٍ is a phrase (شِبْهُ الجُمْلَةِ), a compound consisting of a particle of pulling down (preposition) and a genitive noun

PhraseParticle/NounNoun Particle 
شِبْهُ الجُمْلَةِجَارٌ وَمَجْرُوْرٌاسْمٌ مَجْرُوْرٌحَرْفُ جَرٍّ
PhraseCompoundGenitive NounParticle of pulling down
  
from a springمِن عَيْنٍ=عَيْنٍ+مِن
from a springa springfrom
Surah/Below is the only verse in the holy Quran containing the compoundمِن عَيْنٍ
Verse
  
88-5They will be given to drink from a boiling hot springتُسْقَى مِن عَيْنٍ ءَانِيَةٍ