Tag Archives: rock

Rhodochrosite

rhodochrosite 1Rhodochrosite is a translucent to transparent, ranging in colors from white, to pink, to red. It is a manganese carbonate, found in hydrothermal veins alongside copper, silver, and lead, and can be used as a manganese ore. When exposed to air, rhodochrosite tends to form a dark rind as it oxidizes. It is generally a massive, nodular, or botryoidal rhodochrosite 2form, however the rare transparent rhombohedral crystals can also be found. It has a hardness of 3.5-4 on the Mohs scale, has a white streak, and is soluble in warm hydrochloric acid. Due to its soft nature, and beautiful commonly banded colors, this mineral is often used as a carving medium, but rarely faceted. rhodochrosite 3Its chemical composition is MnCO3. Its name comes from Greek, literally meaning rose-colored.

Pellant, Chris. Rocks And Minerals. New York, Dorling Kindersley, Inc., 2000. Pg 100.

Busbey III, Arthur B.  Rocks & Fossils.  Time Life Books, 1997.  Pg 170.

Chalcopyrite

chalcopyrite 1

Chalcopyrite crystal form

Chalcopyrite is a brassy-colored, copper iron sulfide. It was named by Johann Friedrich Henckel in 1725, from the Greek “chalkos” meaning copper, and “pyrites” meaning to strike fire. It has a green-black streak, yet tarnishes in a variety of iridescent purple, blue, and red. It sometimes goes by the term “peacock rock”. It is often mistaken for pyrite, but is a softer 3.5-4 on the Mohs scale. It is brittle, and can shatter if struck. It has poor cleavage, and fractures unevenly. It can be found in tetragonal crystal form, massive, and even botryoidal.

Chalcopyrite botryoidal

Botryoidal form

This mineral has been mined as a copper ore for thousands of years. Copper mixed with zinc creates brass, but mixed with tin creates bronze – a metal used in tools for ages. It is very common in sulfide veins, high-temperature hydrothermal veins, igneous dikes, and more. When oxidized, or weathered, chalcopyrite may form malachite, azurite, cuprite, and other minerals.

chalcopyrite peacock

“Peacock rock”

Group:  Sulfide.  The chemical formula is CuFeS2.

Klein, Cornelis and Cornelius S. Hurlbut, Jr., Manual of Mineralogy, Wiley, 20th ed., 1985, pp. 277 – 278

http://en.wikipedia.org/wiki/Chalcopyrite

http://www.mindat.org/min-955.html

http://www.esci.umn.edu/courses/1001/minerals/chalcopyrite.shtml