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Identification in the Field and Classroom
Dolomite is slightly harder than limestone. Dolomite has a Mohs hardness of 3.5 to 4, and limestone (composed of the mineral calcite) has a hardness of 3. Dolomite is slightly less soluble in dilute hydrochloric acid. Calcite will effervesce vigorously in contact with cold, dilute (5%) hydrochloric acid, while dolomite produces a very weak effervescence. These differences…
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Dolomitization
Dolomite is very common in the rock record, but the mineral dolomite is rarely observed forming in sedimentary environments. For this reason it is believed that most dolomites form when lime muds or limestones are modified by postdepositional chemical change. Dolomite originates in the same sedimentary environments as limestone – warm, shallow, marine environments where…
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What is Dolomite?
Dolomite, also known as “dolostone” and “dolomite rock,” is a sedimentary rock composed primarily of the mineral dolomite, CaMg(CO3)2. Dolomite is found in sedimentary basins worldwide. It is thought to form by the postdepositional alteration of lime mud and limestone by magnesium-rich groundwater. Dolomite and limestone are very similar rocks. They share the same color ranges of white-to-gray and white-to-light…
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How Much Does Diatomite Cost?
The cost of diatomite depends on its quality, how it will be used, and the preparation effort that has been invested by the supplier. The cost of diatomite that is straight from the mine without processing for use in concrete starts at about $7 per ton. Diatomite from high-grade deposits that has been crushed, sized,…
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Freshwater vs. Saltwater Diatomite
Diatomite forms in marine water and freshwater environments. These origins are an important consideration when a diatomite source is being considered for use. Any use that will be associated with human, animal, or plant contact should come from freshwater deposits. Diatomite from saltwater sources can contain salts that can produce objectionable or toxic effects.
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Diatomite Producers
In 2017, a total of 29 countries produced commercial amounts of diatomite. The United States was the leader, producing an estimated 700,000 metric tons. Czechia, Denmark and China each produced over 400,000 metric tons. Argentina, Peru and Japan produced 100,000 metric tons or more. Other countries that produced at least 50,000 metric tons include Mexico, France, Russia, South Korea, Turkey, and Spain.
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Uses of Diatomite and Diatomaceous Earth
The four main uses of diatomite in the United States during 2017 were filtration (50%), light aggregate (30%), fillers (15%), and absorbents (5%). The properties of diatomite that make it useful in these applications are listed below. Small particle sizeHigh porosityHigh surface areaRelatively inert siliceous compositionLow specific gravity Filter Media The small particle size of…
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Diatom Ooze
When diatoms die, their siliceous frustules sink. In some areas the frustules are not incorporated into the bottom sediment because they dissolve as they sink or dissolve while on the sediment surface. If the sediment is composed of over 30% diatom frustules by weight, it would be called a “diatom ooze” or a “siliceous ooze.”…
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What are Diatoms?
Diatoms are members of a large, diverse group of algae that drift freely in the waters of oceans and lakes. A few types of diatoms live on the bottom of these water bodies and in soils. Most diatoms are microscopic, but a few species are up to two millimeters in length. As a group, diatoms…
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What is Diatomite?
Diatomite is a friable light-colored sedimentary rock that is mainly composed of the siliceous skeletal remains of diatoms. It is a very porous rock with a fine particle size and a low specific gravity. These properties make it useful as a filter media, an absorbent, and as a lightweight filler for rubber, paint, and plastics. When diatomite is…