Staurolite is a mineral often found associated with kyanite in metamorphic rocks, and is formed under similar conditions. The name derives from the Greek words stauros and lithos for stone, giving it a literal meaning of "cross-stone." This mineral forms typical cross-shaped "twins" with a 90- or 60-degree angle between two crystals (Twins are crystals of minerals grown together following specific rules). Staurolite is a hard mineral (Mohs hardness of 7 to 7.5, like quartz) and is resistant to weathering, so loose crystals and twins can often be found in sedimentary deposits of rivers.
Old names for this mineral include "cross-of-Brittany," as this mineral is quite common in the rocks of this French region. In Germany this mineral is also known as Taufstein, as large cross-shaped twins were used as decoration for the baptismal font in the curch. Staurolite has no industrial use, and it's rarely used as gemstone. However, its unusual shape made it an appreciated amulet, especially by Christians. Fairy Stone State Park in Virginia is named after the staurolite found there and a legend tells of how the crystals were formed by the tears of a fairy.