Pearls are not classified as minerals because they are organic in origin. They are formed by two particular species of shellfish called pearl mollusk and pearl oyster as an immune defence against irritants such as parasites. When a parasites enters the fleshy part of the mollusk, it surrounds it with a secreted substance called mother-of-pearl or Nacre. Pearl are undoubtedly the costliest and most important of organic gems. Certification : Laboratory Certified Quality Price : 400-500 500-700 700-1000 & Above