Cochise College           Student Papers in Geology

Geology Home Page                   physical geology  historical geology  planetary  gems           

Roger Weller, geology instructor

diatomaceous earth
by Frederick Bissonnette
Physical Geology
Fall 2011

Diatomaceous Earth

 Diatomaceous Earth

     Diatomaceous earth or DE is a siliceous sedimentary mineral compound formed from microscopic skeletal remains of unicellular plants called diatoms.  The ore is a soft, friable siliceous mineral. It is composed of the skeletons of microscopic plants deposited on the bottoms of oceans and lakes some 100 thousand to 15 million years ago.

     Under the microscope the particles of diatomite show up in a variety of forms such as symmetrical figures resembling disks, rods, cylinders and snowflakes. It is these unique shapes and their rigidity that help interlock themselves to the other particles that makes diatomite such an excellent raw material for the production filtration aids.

     Diatomite forms by the accumulation of the amorphous silica (opal, SiO2·nH2O) remains of dead diatoms such as algae, in lacustrine or marine sediments.

How Diatomaceous Earth appears.


Description: diatomasous-earth.bmp


Description: 6catalina-landslide3712.jpg

R.Weller/Cochise  College

     The fossil remains consist of a pair of symmetrical shells or frustules.  A frustule is the siliceous shell of a diatom. It is composed of two valves, one overlapping the other, like a pill box and its cover

A clam like shape “frustule” of a Diatom (microscopic algea)

Description: diatom-frustules--campylodiscus-sp---80017184f-l.jpg

     Lacustrine is the formation of algae that forms along a body of fresh water such as lakes. DE for short is used mainly in pesticides.  There are other uses such as filters in swimming pools and water purification units.


     The difference between the food grade DE as it is called, and the pool grade DE, is heat.  The pool grade is heated to melt the silica or silicon dioxide to form crystalline structures.  Pool grade DE is between sixty and seventy percent silica free.


     To kill insects with food grade DE sprinkle around affected areas or as a preventive sprinkle DE dust around doors, windows, baseboards, and where pets frequent.

How it kills insects 

     DE kills insects by the tiny razor sharp edges that cut through the insect’s protective coating which then dries up the insect, killing it.  Likewise, if it is applied as a wet powder the insects can ingest the material and it will cut them from the inside killing them.


     DE dust particles are harmful to humans and animals if they breathe it.  If it is ingested in small quantities the human body can rid itself of it.  If consumed by animals in small quantities it can rid the animal of parasites and parasite eggs.


     “Diatomaceous Earth - Experimental Feeding of Codex Food-grade Diatomaceous Earth to Zoo Animals, Richard Smith, Hallwood Inc., Animal Food Specialties, Grand Rapids, Michigan A mixture of feed incorporating 2% diatomaceous earth was sent to three zoos for evaluation.  John Ball Park of Grand Rapids, Michigan; Brookfield Zoos of Chicago Illinois; and Buffalo Zoo of Buffalo, New York.  John Ball and Buffalo Zoos reported that their black bears on the special feed showed a better coat and clearer eyes.  The primates fed at the Brookfield Zoo displayed a pronounced improvement in both appearance and behavior.  Stool samples taken at all three zoos showed an absence of any internal parasites - adult or egg. Parasites in these animals were present prior to using the diatomaceous earth food mixture.”  (


     The Material Safety Data Sheet (MSDS) for DE has the following synonym names:  Celite, Aqua-Cel,  Silica, Flux Calcined, DE, Kieseluguhr.  The chemical name is silica and the chemical formula is SiO2.  Exposure to silica dust may cause cancer, silicosis.  Silicosis is the scaring of lung tissue that can cause shortness of breath or reduce lung function.  Do not breath dust of DE or where an approved respirator when handling and reduce time of exposure.


     DE is composed mostly of silica remains of diatoms.  It also has traces of calcium, sodium, iron, and magnesium.  Food grade DE helps in the absorption of phosphorous and calcium which helps humans maintain healthy nails and hair. (www.articlesfactory)


     On the MOHs scale of hardness the Diatomaceous Earth has a harness of 7, which is the same as quartz.  A lot of industrial usages or pool grade DE has been heated removing sixty to seventy percent of the silica.  Heating the DE not only removes the silica but it causes the DE to re-crystallize leaving mostly quartz’s, which in part, is why most pool filters list the ingredient of their product under DE quartz.


     Simply put Diatomaceous Earth is microscopic algae that died in a body of water a very long time ago.  These tiny single celled animal skeletons were cemented together forming DE.  It has many uses from a natural pesticide to filters for a pool.  Although the raw material is the same for the many different purposes, the usage differs by heat treating, chemically treating, or not, the material dependent on what the end product will be used for.


     There are heath benefits and health hazards with DE, depending on the amount of silica in the product.  For humans and animals there must be less than 3% free silica in the DE or it can be deadly.  The dust of both, natural DE or treated DE is breathed is harmful to humans and animals.  So, know what you are going to use it for and be careful to know the difference between food grade (less than 3% free silica) and pool grade (treated DE). 



Description: diatom1.jpg



Silicon Dioxide diatomite

Description: Silicon Dioxide Type.jpg



Small chunk of Diatomaceous Earth

Description: diatomite.bmp



Resources,  by Gen Wright, October 21, 2011

http://www.   (side of mountain)
550 × 412 - White rock is diatomite. Gray bed looks like a vitric tuff (volcanic ash),  Copyright © Golden Harvest Organics LLC™, 1996-2011 , Diatomite (aka diatomaceous earth) (6.8 cm across),-campylodiscus-sp-/science-mage/80017184f  Diatomaceous Earth Forum | Copyright © 2011 All Rights Reserved

http://www.  , Copyright Notice  2000 - 2011 KITA (KOREA INTERNATIONAL TRADE ASSOCIATION). All rights reserved