The term South Sea Pearls is used for saltwater pearls in the white to gold range that are cultured in the silver-lipped oyster or the gold-lipped oyster. Tahitian pearls are also saltwater pearls but are cultured in the black-lipped oyster.
Technically there are other dark pearls. Pearls from Fiji, and the Cook Islands, and Sea of Cortez for example.
The important thing to remember is that dyed cultured freshwater pearls from China are often deceptively marketed as Tahitians. However, I think you have a strand of Tahitians there.
Edit: Katbran has a good suggestion. Get clear, in-focus photos on a white background, and no flash. Only then can you see the overtones of the pearls.