Melanite

Melanite is the jet-black, titanium-rich variety of andradite garnet, part of the calcium-iron “ugrandite” group alongside grossular and uvarovite. Its opaque, near-metallic darkness comes from titanium substituting for iron in the crystal lattice, sometimes reaching over 11% TiO2, placing melanite in solid solution toward schorlomite and morimotoite. Chemically it is expressed as Ca3(Fe3+,Ti)2(SiO4)3, and despite its black color it retains the high dispersion typical of andradite, occasionally producing an unexpected sparkle beneath the dark surface. Crystals form in the isometric system, most often as sharp trapezohedra or dodecahedra with a glassy to submetallic luster, occasionally as fine druzy crusts.

Unlike gem-green demantoid or golden topazolite, which favor serpentinites and chlorite schists, melanite is characteristic of alkaline igneous rocks such as nepheline syenite and phonolite, and also occurs in contact-metamorphosed limestone skarns alongside grossular. Classic European localities include the volcanic districts around Vesuvius and the Alban Hills in Italy, the Ala Valley and Elba in Piedmont and Tuscany, the Kaiserstuhl in Germany, and Arendal in Norway; further afield, notable occurrences include Magnet Cove in Arkansas, Iron Hill in Colorado, and the Oka alkaline complex in Quebec. Facet-grade melanite crystals large and clean enough for cutting are rare and come almost exclusively from three sources: the Nioro du Sahel district in Mali, Chihuahua in Mexico, and the Dallas Gem Mine in San Benito County, California — the same deposit famous for gem-quality benitoite.

Collectors seek melanite for its striking contrast with the more familiar red and orange garnets, its historical role in Victorian mourning jewelry, and its mineralogical link to the andradite-schorlomite series, which makes fine, well-formed crystals valuable reference specimens for the study of titanium substitution in silicate garnets. Sharp, lustrous dodecahedral crystals on matrix, especially from classic alkaline-rock localities, are prized both by systematic collectors building a complete garnet-group suite and by those drawn to melanite's uniquely somber, light-absorbing black beauty.