Classification of Minerals(5. Carbonates, Nitrates and Borates)
5. Carbonates, Nitrates and Borates
CO32-, an anionic complex, is a basic unit of carbonates. Nitrates and borates are similar to carbonates in their structures and properties. They also have strongly bonded units of NO3- and BO33-.
In general, carbonates are transparent, soft, soluble and lightly colored with a white streak. They tend to occur in oxidizing environments, in sedimentary rocks or in carbonatite igneous intrusions. They include the calcite group (calcite, magnesite, siderite, rhodochrosite, smithsonite), the aragonite group (aragonite, witherite, strontianite, cerussite), the dolomite group (dolomite, ankerite), malachite and azurite.
Nitrates include nitratite and niter. Nitratite is isostructural with calcite and has similar physical properties. Niter is similar to aragonite in structure. Nitratite and niter are relatively softer and less dense than calcite and aragonite. Boron is not a common element on the earth's surface, so borates are scarce and limited in their distribution. They include kernite, borax, colemanite and ulexite. Borates are used in making special glass.
Weloganite Quebec, Canada
Weloganite is rare so its localities are limited. Francon Quarry, Quebec, is the most famous place where it is found.
Aragonite Donghae, Korea
Aragonite is polymorphous with calcite. It is less stable than calcite under most natural conditions, where it tends to change into calcite.
Malachite Zaire
Bright green color and botryoidal forms characterize malachite. It is used as an ornamental and gem mineral.
Siderite Daegu, Korea
Siderite is named after ‘sideros’, meaning iron in Greek.
Calcite Morocco
Calcite crystals, grown within cavities of sedimentary rock, are colored in pink, like rose. This pink color is not caused by major elements, but by impurities of trace elements.
Calcite USA
Calcite USA
Calcite Brazil
Canine tooth-like crystals developed in limestone.
Colemanite USA
Colemanite is brittle, colorless or white-colored borates. It has vitreous luster.
Strontianite Donghae, Korea
Strontianite is an ore mineral of strontium. It is used for making flames in fireworks.