Chiastolite is a variety of Andalusite that contains a black cross pattern when seen in a cross-section.  It is also known as the Cross Stone.  In ancient times, this stone was said to bring health and harmony.  Chiastolite is a highly protective stone, often worn to guard against negative energies.  It encourages creative thinking and problem-solving by getting rid of old thought patterns that have been keeping us from moving ahead.