Hararite

Hararite is a rare mineral that belongs to the calcite group of carbonate minerals. Its chemical formula is CaCO₃·0.5H₂O, indicating that it is a lightly hydrated form of calcite. The crystal system is trigonal, but well‑formed crystals are uncommon; the mineral is usually found as friable, powdery masses or tiny, translucent crystals. The color range of hararite includes white to grayish white, with occasional pale blue or green tinges, and it displays a silky to waxy sheen. The mineral has a Mohs hardness of 3 to 3.5, making it relatively soft, and its specific gravity is 2.71 g/cm³. On the Mohs scale, it is similar in hardness to orthoclase feldspar, but distinct in its mineralogical properties.

Hararite was first described in the early 20th century from a deposit near Harar, a historic city in eastern Ethiopia. It is believed to form by the replacement of calcite in evaporitic environments, or through the alteration of other carbonate-bearing rocks under the influence of groundwater with a high sodium content. The mineral is usually associated with other evaporite minerals such as sylvite, halite, and carnallite, and it can occur in veinlets within limestone. In recent years, small quantities have been reported from ancient salt mines in Europe and North Africa, though the type locality remains the most studied.

Because of its rarity and the difficulty of obtaining pure specimens, hararite has not been extensively studied in modern mineralogy. Existing literature focuses on its crystallographic characteristics and its place in the evaporite assemblage. The mineral is named after the city of Harar, reflecting its discovery location. Hararite is of interest mainly to collectors and mineralogists who study carbonate variations in evaporitic contexts.