The mineral pyrope (from the Greek pyropos "fiery") is an island silicate from the garnet group and has the chemical composition Mg3Al23.
The mineral crystallizes in the cubic crystal system, often in (rounded) grains. It also occurs in aggregates. Pure pyrope, e.g. from the white slates of the Dora Maira massif, is colorless. Due to the incorporation of iron (Fe2+) instead of magnesium (Mg), the coloration of pyrope ranges from pink to blood-red and black-red, often with a tinge of brownish.
One of the earliest mentions of garnets as an ornamental stone can be found in the Bible in the Book of Exodus as a stone on the breastplate of the high priest Aaron. In his work Naturalis historia, Pliny the Elder summarized a number of red minerals under the term carbunculus, including garnets. A further differentiation of this group into three subgroups (ruby, spinel and garnet) was made by Albertus Magnus around 1250 in his work De mineralinus et rebus metallicus. The modern name pyrope is derived from the Greek pyropos "of fiery appearance", which alludes to the red color.
As late as the 18th century, various minerals were referred to as garnet on the basis of their external characteristics, including leucite, for example. This changed when the systematic chemical analysis of minerals began. In the course of these investigations, Martin Heinrich Klaproth was the first to determine the composition of what was then known as "Bohemian garnet" designated pyrops.
The crystal structure of garnets was elucidated by Georg Menzer in 1929 and the first synthesis of pure pyrope was achieved by Loring Coes junior at 30,000 bar and 900 °C in the mid-1950s using newly developed high-pressure presses from the Norton Company (Massachusetts, USA). Synthetic pyrope from Coes' laboratory was used by Skinner in 1956 to determine the physical properties (lattice constant, refractive index, density) of pure pyrope and by Anna and J. Zemann five years later for the first structural refinement of pyrope.