The metal impurity that makes rubies red and emeralds green is chromium. Chromium is a trace element that can be found in various minerals, including corundum (which is the mineral that forms rubies) and beryl (which is the mineral that forms emeralds). When chromium is present in corundum, it causes the mineral to absorb certain wavelengths of light, giving the ruby its characteristic red color.
Chromium, an element known for its ability to impart vibrant colors to gemstones, plays a pivotal role in determining the hues of certain precious stones, such as rubies and emeralds.
In rubies, the presence of chromium within the crystal structure of corundum, the mineral family to which rubies belong, creates the iconic deep red color. Chromium ions, substituting some aluminum atoms within the corundum's lattice, lead to the absorption of specific wavelengths of light. This absorption phenomenon results in the manifestation of the ruby's vivid red hue, ranging from intense crimson to slightly purplish or orangish tones. The strength and purity of the red coloration often depend on the concentration and distribution of chromium atoms within the corundum matrix.
Similarly, chromium is responsible for the verdant green hue in emeralds, which belong to the beryl mineral family. In the case of emeralds, trace amounts of chromium, along with vanadium, nickel, and iron impurities, work in conjunction to imbue the gemstone with its renowned green color. However, the exact mechanisms and combinations of trace elements responsible for the precise shade of green in emeralds can vary, leading to variations in the stone's coloration from light to dark green, with differing levels of saturation and brilliance.
The subtle interplay of chromium's presence within the crystal lattice of corundum and beryl minerals dictates the distinctive and prized colors exhibited by rubies and emeralds, contributing to the allure and value of these gemstones in the realm of jewelry and adornment.