The backing for the stone is polished silver, so the transparent stone will always shine, no matter what the background for the necklace is (dark or light).
Tourmaline hardness in Mohs scale is 7 - 7,5, that makes it suitable for any kind of jewellery. It is very durable, transparent and beautiful. It comes in a rainbow of colours (according to an old Egyptian legend, tourmaline passed over a rainbow on its journey from the centre of the Earth). Blue colour is probably the most rear and desirable, though pink and green together in one stone is quite sought after too (then it is called "watermelon" tourmaline).