Smithsonite, also called zinc spar, is a carbonate of zinc (ZnCO3), and is a mineral ore. Previously, it was thought to be Hemimorphite, till it became known that the two were different minerals. Since the appearance of these two is similar, the word calamine was used to describe both, causing some confusion. Its Mohs hardness is 4.5.
Derivation of Name
During 1832, François Sulpice Beudant so named this mineral to honor English mineralogist James Smithson (c. 1765–1829), who was the first to identify it during 1802 and whose legacy founded the Smithsonian Institution.
Smithsonite is a secondary mineral, found in the oxidation or weathering regions containing deposits of zinc ore. Occasionally it is found as a replacement body among rocks of carbonate and may thus form zinc ore. It is usually found along with Hydrozincite, Hemimorphite, Cerussite, Malachite, Willemite, Azurite, Anglesite and Aurichalcite. It fashions two partial solid solution chains. While replacement of manganese results to Rhodochrosite, with iron, it results to Siderite.
Smithsonite is among the not so well known and exceptional stones, making a favorite of collectors only. It finds infrequent use in jewelry designs. Additionally, it is quite soft and delicate to be utilized for most kinds of jewelry, despite having almost the same hardness as turquoise or opal, the two which are frequently incorporated in jewelry.
Visible crystals of Smithsonite are rarely found in nature. Just two locations are known for producing big, worthwhile crystals: Broken Hill, Zambia and Tsumeb, Namibia. Practically all other findings of Smithsonite are botryoidal-like or spherical in shape. A number of rounded forms come with a soft or shining light effect.
This mineral belongs to the family of Calcite minerals that form a group of connected carbonates which are isomorphic to each other. Many of their physical properties are similar and may partly or completely substitute one another to form a solid solution series. Each and every member of calcite collection crystallizes in the trigonal system, has flawless rhombohedral cleavage and demonstrates powerful double refraction in translucent rhombohedrons.
White, green, apple-green, gray, yellow, pink, purple, blue, brown and bluish gray.
On Mohs scale 4.5