What is a spectroscope used for in gemstone testing?

• A. To measure gemstone weight.
• B. To determine hardness.
• C. To assess fluorescence under UV.
• D. To observe absorption lines/bands in a stone's spectrum, aiding identification.

Answer: (D)

A spectroscope reveals how a gemstone absorbs light and shows the absorption lines and bands in its spectrum. Those spectral features act like a fingerprint for the mineral, tied to its crystal structure and trace elements. By comparing the observed pattern to known spectra, you can identify the gemstone and sometimes spot specific varieties or treatments. This makes it a powerful identification aid, more informative for distinguishing stones than simply weighing them or testing hardness. Fluorescence under UV is a separate observation, while a spectroscope focuses on the absorption spectrum produced by light interacting with the gem.