Amethyst enjoyed great popularity among the ancient Egyptians during their 'Middle Kingdom' period, which started over 4000 years ago and lasted for almost 400 years.
The famous Egyptian king Tutankhamen wore a bracelet inset with a large Amethyst Scarab.
Purple was a rare color in nature and ancient Egyptians saw purple as an intermediate color, having turned from red into a particular shade of blue. The Egyptians believed Amethyst had a strange origin, from between worlds and that it had the power to protect you from harm by transforming bad energies (red) into something more benevolent (blue).
The creation process of shaping and drilling amethyst would have been time-consuming work, and thus finished objects produced would have had a relatively high value.
Amethyst was extremely popular for seals and scarabs in Egypt, particularly in the New Kingdom. The vast majority of Amethyst was used for the creation of beads and scarabs. Scarabs themselves had a major role in ancient Egypt. Due to the way scarab beetle came in to life, it was often believed to come in to life from nothingness as its eggs were laid in their dung balls, and thus were never visible until already born. It's behavior was associated with the sun's movement through the sky. This made scarabs symbols of life and regeneration, and as amulets they could transfer these powers.
Most of the representation is believed to be attributed to the scarab beetles religious significance in the form of Khepri, a sun-god which was an aspect of Ra. Symbolizing creation, growth, rebirth. Its transformation gave it form. A translation would be to make oneself, or to rebuild oneself.
All this earned the Scarab it's own deity and countless representations throughout the Ancient Egypt in the forms of seals, amulets, jewelry and other artifacts.