Goldstone is manmade glass with flecks of copper suspended in it. Its invention occurred by accident in seventeenth-century Venice by the Miotti family. The glass is made in a reducing furnace with copper salts added, this "smelts" the copper salts back to copper, which then crystallizes.
As a healing stone, it is the stone of "ambition and drive" and has a gently uplifting quality. The metaphysical properties of copper are said to be the ability to aid the circulatory system, help strengthen bones and fight arthritis pain.
Beautiful and useful too! Pendulums are used much the same way as applied kinesiology or muscle testing to help determine the answer to a question.