This is an unusual green aventurine and Japanese saltwater Akoya cultured pearl opera length necklace.

The pearls are 5.50mm and have good luster with light rosy overtones. The aventurine is a medium green with darker green flecks, they also measure 5.50mm. 

The clasp is in sterling silver with engraving and milgrain. It is stamped "SILVER" for sterling silver. Total length is 32 inches. Very rare and unique, mid-century. 

All pearls are truly vintage and have only been lightly cleaned and restrung.