Which trace elements are responsible for the color of blue sapphire?

Blue sapphire's iconic color primarily arises from the presence of specific trace elements, particularly titanium and iron. In the case of blue sapphire, when corundum (the mineral that forms sapphire) crystallizes, titanium ions replace aluminum within the crystal lattice. Simultaneously, iron can substitute for aluminum as well.

The interaction between these two trace elements plays a crucial role in producing the characteristic blue hues. Titanium typically absorbs light in the red part of the spectrum, while iron can contribute to the absorption bands in the yellow and green regions. The combinational effect of these absorptions leads to the rich blue color that is highly valued in blue sapphires.

Moreover, the presence of these elements can influence the saturation and tone of the sapphire's color. As a result, understanding the role of titanium and iron in sapphires is essential for anyone studying colored gemstones, as it explains not just the color but also the quality characteristics that are considered when grading and valuing these precious stones.