Sapphire is blue with black streaks across it. It shares textures with ruby and turquoise, but with different colors. Therefore, under the lights of different rare ores, it can appear to be ruby or Turquoise.
Sapphire can be sold for $48. It is really useful to new players, but to other players, not so much. However, getting a lot of these can be pretty good, as 11 sapphires can add up to the price of one Uranium. Also, rare ores can replace Sapphire over time, making them useful to leave behind.