What is Kentucky's state gemstone?

The state gemstone of Kentucky is turquoise. This gemstone is not only valued for its beauty but also holds historical significance as it has been used by various cultures for centuries. Turquoise is appreciated for its striking blue color and is often associated with healing and protection. In Kentucky, it symbolizes the state's natural resources and cultural heritage, making it a fitting choice as the official gemstone.

The other options, while they may be well-known gemstones, do not have the same specific designation in Kentucky. For instance, diamonds and emeralds are certainly prized gemstones, but they are not representative of Kentucky's identity or natural resources in the same way turquoise is. Opals are beautiful and unique, but they too lack that connection to Kentucky's state symbolism. Thus, turquoise stands out as the correct answer, emblematic of the state's proud heritage and connection to nature.