Amazonite

Amazonite is a green to blue-green variety of microcline, a potassium feldspar, and is also called amazonstone. Wikipedia says it has been worked into jewellery for more than three thousand years and was first described as a distinct mineral in the eighteenth century. Cunningham classes it as a receptive stone ruled by Uranus and the element earth, and says gamblers wear it for money luck and that anyone taking a chance may wear it to help the venture succeed. Hall describes it as a filtering stone that calms, evens out masculine and feminine energies, and shields against geopathic stress and electromagnetic pollution; she places its healing work with the heart and throat chakras. These uses are the claims of the magical writers, not tested properties of the mineral.