### antacid:

Calcium carbonate
* Some calcium carbonate is derived from oyster shells.
* are present as nodules, masses, or coats on ped faces.
* comes from many sources, most of which have a biological origin
  - in a chewable form and is marketed by a number of different companies
* common agent, the same one used in commercial cement.
* contains the highest amount of elemental calcium
  - percentage of calcium
* derived from high-purity limestones or marbles is used in medicine.
* good antacid and provides calcium, which is desirable
  - but it also provides calcium, which is desirable
  - supplement for calcium and phosphorus control
* interferes with the absorption of chromium.
* is also an important contributor to some geological changes
  - notorious for creating gas, bloating and constipation
* is an antacid
  - ingredient of some toothpastes and toothpowders
  - associated with acid rebound
  - chemical compounds
* is considered a fairly nontoxic substance and recovery is quite likely
  - substance, so recovery is quite likely
  - slightly soluble, while calcium sulfate is moderately soluble
  - currently the best and least expensive form of calcium supplement available
  - derived from limestone, chalk, and other calcium-rich materials
  - dissolved by stomach acid
  - electrolytes
  - inexpensive, but is absorbed best when taken with food
  - inorganic compounds
  - insoluble in water
  - ionic compounds
  - less expensive
  - lightfast
  - more rigid than calcium phosphate
  - polymorphic with calcite and aragonite being the most common natural forms
  - precipitated forming fine white deposits at the bottom of the pools
  - proven to be highly alkaline
  - salt
  - secreted by the mantle, a fold in the epidermis, forming the shell
  - soluble in concentrated mineral acids
* is the active ingredient found in some antacids
  - basis of sea shells and concrete
* is the cheapest and has the most elemental calcium
  - safest
  - calcium and also the most difficult for the body to absorb
  - least expensive calcium supplement available and the most widely available
  - main compound found in egg shells
* is the most common and inexpensive form of calcium
* is the most common form of calcium in supplements
  - kind of carbonate cement
  - mineral in invertebrates but some do have calcium phosphate
  - type of scale deposit in cooling and boiler systems
  - concentrated form of calcium and is also the least expensive
  - widely used form of calcium
  - natural source that bonds the stone
  - primary source of scale in cooling and boiler water systems
  - same white buildup that can be seen on dry coffee pots
  - sole parameter for determining the corrosivity of a water
  - thought to be best absorbed when taken with a meal
* is used as a building material
  - tablet binder
  - buffer
  - to prevent and to treat calcium deficiencies
  - usually the main cause of hard water
  - very abundant and usually mined
* key building block for the shells and skeletons of many marine organisms.
* makes bones stiff and hard
  - the egg shell strong, but without it, it gets soft and rubbery
  - up the skin of all starfishes
* mineral substance found in limestone and other calcareous rock formations.
* natural form of calcium.
* needs to be taken with meals to ensure absorption.
* neutralizes the acid and relieves heartburn immediately.
* occurs as masses or concretions
  - naturally as limestone and chalk
* precipitates out of solution once the soil begins to dry.
* provides the most calcium per milligram.
* reduces the acidity, or pH, in paper and thus improves paper lifetime.
* requires an acidic environment in order to be absorbed.
* solid mixture.
+ Alkali, Uses of common Alkalis: Chemistry
  * Calcium carbonate' is a chemical compound, with the chemical formula CaCO3. It is a common substance found as rock in all parts of the world, and is the main component of seashells, snails, and eggshell. Calcium carbonate is usually the main cause of hard water. It is used as a calcium supplement or as a treatment for antacid, but too much can be bad for your health.
+ Calcium, Uses, As chemical compounds: Alkaline earth metals
  * Calcium is part of calcium oxide. Calcium carbonate is used as a calcium supplement. Calcium permanganate can be used as a rocket propellant.
  * Note  that  gypsum, chalk, limestone and marble are calcium compounds which can be obtained through mining. Calcium carbonate is very abundant and usually mined. So if you like rewrite and move the article to reflect that.