Blue olives are a type of Ceylon olive (Elaeocarpus serratus) indigenous to Sri Lanka. It grows in the west and centre of the island in medium size trees with leaves similar to the avocado. Known locally as Nil Veralu (in Sinhala), this tropical fruit is found across the Indian Subcontinent, Indo-China and South East Asia.

While the green variety of veralu looks just like the common green olive (Olea europaea), the blue olive is almost perfectly spherical in shape with a bright blue edible skin.  

What Does Blue Olive Taste Like?
The blue olive has a firm green flesh with a pasty, avocado-like texture. It is astringent when unripe, and slightly sour when ripe. In its native home in Sri Lanka, varieties of Ceylon olives are used in ways very different to how Mediterranean olives are typically used.