# Diatomaceous Soils and Advances in Geotechnical Engineering--Part I
## 2 Evolution of Concepts Surrounding Diatomaceous Soils
### Diatomites
In civil engineering, diatomites are described as sedimentary rocks of considerable porosity and large specific surface area [62]. A high-purity diatomite will have between 80% and 99% biogenic SiO\({}_{2}\)[63]. The existence of rocks with diatoms can even be differentiated from what is defined as diatomite, taking into account possible variations in the matrices that host the fossils. Thus, Ref. [67] report, for example, \"diatomaceous shales\" and define them as \"soft rocks\". The \"Diatomite. U.S. Geological Survey, Mineral Commodity Summaries\" ([PERSON], 2008) and \"Diatomite\" ([PERSON], 1994) [64] state that world diatomite reserves are estimated at 920 million tons, of which 250 million tons are in the United States. In 2007, the major producing countries were the U.S.A. (41%), China (21%), Denmark (12%), Japan (6%), France (4%), and Mexico (3%), with other smaller producers such as Germany, Spain, Chile, Romania, the Czech Republic, and Peru with a production per country of less than 3%. In the U.S.A., the largest diatomite deposits are located in California, Nevada, Oregon, Washington, and Arizona. In Europe, they are found in France, Denmark, Spain, Germany, and the Czech Republic. In Africa, they are found in Algeria, South Africa, and Kenya. In Asia, they are found in Japan, South Korea, and China. In Latin America, they are found in Mexico, Brazil, Argentina, Chile, Peru, and Costa Rica. In the Colombian context, there are records of deposits in areas such as Cartago--Obando--La Victoria and Zarzal (Valle del Cauca), Tunja--La Uvita--Chinavita and Dicata (Boyaca); laguna \"La Herrera\" and Tibagota (Cundinamarca); and Fronting (Antioquia), among others [64]. In the Department of Boyaca, the deposits are located in intra-mountain sedimentary basins that correspond to synclinal structures, which allowed the formation  
Figure 5: Proposed classification of sediments with the presence of diatoms [63]. of lakes, the proliferation of diatoms, and the formation of diatomites. Thirteen diatomite occurrences have been identified: eight in the municipality of Siachoque, three in Tunja, and two in Chivata [64]. On a regional scale in Mexico, the most important deposits are located in the state of Jalisco, where 99% of the exploitation occurs. The main identified uses of diatomite are as a filter, decolorizer, insulator, absorbent, fertilizer, insecticide, filler material, and source of silica [58]. As a filter, it is applied to clarify and purify liquids in chemical, metallurgical, food, pharmaceutical, beverage, and petroleum processes. Due to its porous structure and inert chemical composition, diatomite retains dissolved, suspended, or colloidal particles from the filtered liquid without modifying the physical-chemical characteristics of the final product [64]. The presence of frustules gives diatomites different physical properties (low density and large specific surface area) from those associated with claystones or sandstones. In addition, the mechanisms through which these properties are imposed have yet to be fully understood, particularly from a microscopic perspective. Existing research has provided a partial understanding of the behavior of diatomites, establishing that their index properties are less important than their engineering properties. How the presence of frustules affects index properties has not yet been fully elucidated [14].