This type of pistachio kernel is normally harvested one month earlier (in July and August) before it becomes completely ripe. Kal means raw in Persian.  Unripe crops tend to yield better green color and this is the difference from regular pistachio kernel. 

There are 4 categories of Kal Pistachio Kernel according to the % of green color kernels : 

• Superior grade: 90% of the total quantity is green 
• Grade1: 80% of the total quantity is green 
• Grade2: 70 % of the total quantity is green 
• Grade3: 60% of the total quantity is green