First report of a nephrite deposit from Somaliland, Africa: Characterization and geological and archaeological implications

Abstract

Nephrite jade is of wide interest, not only for its value as a highly valued precious stone, but also for its significance in tracing geological and petrological processes. Here, we report the first discovery of a nephrite deposit in Africa, located in Somaliland. Field investigations revealed that two open nephrite pits at Goodieood and Laasmacaane are composed of a series of discontinuous vein-shaped nephrite bodies stretching for ∼2 km and defining a nephrite belt. Dolomitic marble and epidote-amphibole are the major rock types in this nephrite belt. Most of the nephrites show grayish green color, while a few are grayish white to light-grayish green, with an occasional brownish rind mainly in nephrite gravels from the secondary deposits. The nephrite is composed of tremolite and actinolite with minor diopside, pargasite, edenite, and apatite. Most nephrites display fine fiber microstructures, and the tremolite-actinolite aggregates show crystallographic preferred orientation. Parallel to the nephrite bodies, epidote-amphibole rocks appear as a metasomatic dark-colored boundary zone, composed mainly of actinolite-tremolite, epidote, and titanite with minor rutile, pargasite, edenite, diopside, and zircon. The dolomitic marble displays dolomite replacement partially by antigorite. Textural observations suggest a sequence from Na-, Al-, and Fe-rich toward Mg-rich compositions, leading to the possibility of prospecting for white nephrite. The various features suggest that the deposit belongs to a fluorine-bearing Ca-Fe-P fluid-dominant skarn. This deposit is estimated to have more than 1000 tons of nephrite jade reserves and has important significance for the exploration for more economic nephrite deposits in Africa, South America, and even Antarctica, as well as potentially important archaeological implications in establishing a connection between the nephrite jades and materials for the Hargeisan lithic industries, as part of the social development in eastern Africa. Comparison with a typical white nephrite deposit in Saidikulam provides insights into the formation of white and nonwhite nephrites.