Prase

Prase is a leek-green variety of macrocrystalline quartz, its color owed not to its own lattice but to dense fibrous inclusions of actinolite (an amphibole) and, in some deposits, hedenbergite (a pyroxene) locked inside the crystal. Because these fibers interfere with normal growth, prase crystals often develop unusual elongated, tapering, or cigar-like habits instead of the classic hexagonal quartz prism, a quirk collectors use to help pinpoint origin. It forms almost exclusively in skarns, where hot silica-rich fluids from cooling igneous intrusions react with carbonate rocks, commonly alongside andradite garnet, epidote, hematite, and ilvaite.

The type locality is the Island of Elba, Italy, particularly around Rio Marina and Porticciolo, historically prized for fine leek-green material. Equally famous is Serifos in the Greek Cyclades, whose slender, spindle-shaped crystals with hedenbergite or actinolite inclusions are considered the classic collector's prase. Other important sources include the Sinerechenskoe skarn near Dalnegorsk, Russia, with its sharp tapered crystals on andradite matrix, the Imilchil area of Morocco, and historic German finds near Breitenbrunn in the Erzgebirge, alongside occurrences in China, Nepal, and the Ural Mountains.

True crystallized prase is genuinely scarce compared to ordinary quartz, and specimens with well-formed, lustrous, richly colored crystals on matrix are actively sought by systematic quartz collectors and skarn-mineral enthusiasts alike. Its combination of striking green color, unusual crystal morphology, and tightly restricted locality list makes prase a distinctive addition to any serious mineral collection.