![Text Box: Diatomite is NOT chalk, but it is like chalk in its general appearance. Similar to chalk, Diatomite was formed from the skeletal remains of micro-organisms millennia ago. Diatomite is the mineral name for the hardened sediment formed by the dead bodies of microscopic algae referred to as diatoms. On the other hand chalk, the common name for the mineral “Calcite”, was formed by a different kind of alga altogether, called a “coccolithophore”.
Besides the fact that they are both algae, further similarities shared by the two organisms are that:
They are both members of that very broad group known as plankton.
More specifically both are classified as phytoplankton[1].
Furthermore, due to their microscopic size, both diatoms and coccolithophores may be further classified as nannoplankton[2].
Accordingly, both organisms belong to the Phylum, Protista,
but that is where the taxonomic similarity ends…](Page%202%20part%201_files/image001.gif)
Is Diatomite Chalk?
Division: Chrysophyta,
Class: Bacillariophyceae
http://www.answers.com/topic/diatom
whereas, Coccolithophores are “Haptophytes” belonging to the
Class: Prymnesiophyceae
http://www.answers.com/topic/coccolithophore
An interesting physiological distinction is that Coccolithophores selected calcium as a shell-hardener. Bonded with carbon and oxygen their formations are chemically known as Calcium Carbonate (CaCO3), the main component of limestone, as well. Their special calcium carbonate scales (or plates) called coccoliths, are important microfossils. Coccolithophores are exclusively marine, and are found in large numbers throughout the surface euphotic zone of the ocean. Emiliania huxleyi is a good example of a global coccolithophore.
However, the diatoms chose silicon to form their little skeleton. Silicon bonded with oxygen, results in "silica” (chemical formulation, = SiO2, aka, “Silicon Dioxide”). Silica is the same material that is used to make glass for automobile windshields and windowpanes for houses. Diatomite, therefore, will not fizz when you put a drop of hydrochloric acid on it. Contrastingly, chalk fizzes because it releases carbon dioxide (CO2).
[1] http://www.amonline.net.au/exhibitions/beyond/phytoplnkton/index.htm
[2] http://www.epennypress.com/Words_Starting_with_N/name_part_narine/nannoplankton_definition.html