Solubility, Calcite and Limestone.
Carbonates. In nature, carbon atoms join with oxygen to form the carbonate ion, CO3. These ions combine with metal cations to form carbonate minerals. These minerals are commonly formed in sedimentary and oxidizing environments. The carbonates fall into three groups: the calcite group, the dolomite group, and the aragonite group. The copper carbonate minerals, azurite and malachite, are the only important economic carbonates. Minerals of the carbonate class: 1  Are transparent Some rocks contain carbonate minerals and the acid test can be used to help identify them. Limestone is composed almost entirely of calcite and will produce a vigorous fizz with a drop of hydrochloric acid. Dolostone is a rock composed of almost entirely of dolomite. Calcite and other carbonate minerals have a low resistance to weathering and can be attacked by acids in natural waters and soils. When testing material that has been exposed at Earth's surface it is very important to test unweathered material. A fresh surface can usually be obtained by breaking the rock. The most common are calcite or calcium carbonate, CaCO 3, the chief constituent of limestone (as well as the main component of mollusc shells and coral skeletons); dolomite, a calcium-magnesium carbonate CaMg(CO 3) 2; and siderite, or iron (II) carbonate, FeCO 3, an important iron ore. In geology and mineralogy, the term carbonate can refer both to carbonate minerals and carbonate rock (which is made of chiefly carbonate minerals), and both are dominated by the carbonate ion, CO 2− 3. Carbonate minerals are extremely varied and ubiquitous in chemically precipitated sedimentary rock. Carbonate is found frequently in geologic settings and constitute an enormous carbon reservoir. Calcium carbonate occurs as aragonite and calcite. The carbonate minerals form the rock types: limestone, chalk, marble, travertine, tufa, and others. Calcium carbonate has been found in some mines to be 99.2% pure. In tropic settings, the waters are warm and clear. Calcium carbonate is the active ingredient in agricultural lime, and is created when calcium ions in hard water react with carbonate ions creating limescale. It is commonly used medicinally as a calcium supplement or as an antacid, but excessive consumption can be hazardous. To most geologists, the term acid test means placing a drop of dilute (5% to 10%) hydrochloric acid on a rock or mineral and watching for bubbles of carbon dioxide gas to be released. The bubbles signal the presence of carbonate minerals such as calcite, dolomite or one of the minerals listed in Table 1. Calcite and other carbonate minerals have a low resistance to weathering and can be attacked by acids in natural waters and soils. When testing material that has been exposed at Earth's surface it is very important to test unweathered material. A fresh surface can usually be obtained by breaking the rock. Solubility: Of all the common carbonate minerals, calcium carbonate is most soluble. The solubility of CaCO 3 depends on the polymorph. At 25 degrees, the K sp for calcite and aragonite (the most common polymorphs of CaCO 3) are 10 -8.48 and 10 -8.34, respectively. Click here to see solubility product constants for other minerals. Calcite is one of the most abundant of the non-silicate minerals. Pure calcium carbonate is colorless but, because it dissolves in acidic water and can recrystallize with different inclusions, calcite has many forms and colors in nature. As a result, the three calcium carbonate minerals-calcite, aragonite and vaterite-are among the most important rock-forming minerals. Rocks are not the only calcium carbonate deposits in nature, most stretches of water and countless plants and animals contain huge amounts of calcium carbonate.  Carbonate minerals are those minerals containing the carbonate ion: CO 3 2− . 
http://www.mineralogy4kids.org/mineral-group/carbonates http://geology.com/minerals/acid-test.shtml https://en.wikipedia.org/wiki/Carbonate https://en.wikipedia.org/wiki/Calcium_carbonate http://geology.com/minerals/acid-test.shtml http://butane.chem.uiuc.edu/pshapley/Environmental/L26/2.html http://www.ima-europe.eu/about-industrial-minerals/industrial-minerals-ima-europe/calcium-carbonate https://en.wikipedia.org/wiki/Carbonate_minerals
what minerals are carbonate