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The main mineral composition of diatomite is opal
May 11, 2018

The main mineral composition of diatomite is opal, and it contains clay (kaolinite, water mother and a small amount of glue ridge), carbonaceous (organic matter), iron (limonite, hematite, pyrite), carbonate minerals (calcite, dolomite, small amount of siderite), stone, muscovite, hedlite, feldspar.

1. Opal Si02nH202, clay minerals and charcoal

Clay minerals and carbon are the main associated minerals in diatomaceous earth. Clay minerals are microscale and distributed around diatoms. When clay minerals are the main components, clay minerals play a role in cementation of diatoms. The carbonaceous texture is characterized by point, lump or lamellar intergrowth with diatomaceous earth, and the carbonaceous matter is peat and lignite with low metamorphism and still retain plant structure.

Diatomite is a kind of rock with biological structure. It is mainly composed of 80~90%, some of which consist of more than 90% diatoms. The main consumption of silica in seawater and lake water is diatom, which constitutes diatom ooze.  Diatomaceous earth is formed in the petrochemical stage during diagenesis.

The diatom shell is composed of opals. Diatoms absorb colloidal silica in water and grow into opals gradually.

The more diatom content in diatomite, the less impurity, the lighter the color and the lighter the quality. The proportion of the diatom is generally in 0.4-0.9g/cm3. Because the diatom body has a large number of cavities, the diatomite has porous structure, the porosity of the diatomite is 90-92%, the water absorbability is strong and the tongue is sticky, because the diatom particles are fine and the diatomite is fine and slippery.  Diatomite is insoluble in acid (HCl, H2SO4, HNO3), but soluble in HF and KOH.

Diatomite is a biogenic siliceous sedimentary rock, mainly composed of the ancient diatom body. Its chemical composition is mainly SiO2, and contains a small amount of Al2O3, Fe2O3, CaO, MgO, K2O, Na2O, P2O5 and organic matter.

Diatoms in diatomaceous earth have many different shapes, such as disc, needle, cylinder, feather, etc. The loose density is 0.3-0.5g/cm3, the Moir hardness is 1~1.5 (diatom skeleton particle is 4.5-5mm), the porosity reaches 80-90%, it can absorb water of its own weight 1.5-4 times, it is a bad conductor of heat, electricity and sound. The melting point is 1650-1750 C and the chemical stability is high. Besides dissolving in the hydrofluoric acid, it is insoluble in any strong acid, but can dissolve in strong alkali solution. 

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