# Micromechanical Characterization of Diatom Frustules of Multiple Origin
## 3 Materials and Methods
### Diatomaceous Soils  
The particles analyzed are frustules from diatomaceous soils located in Colombia, Mexico, and Peru. These were selected due to their evident morphological differences, a product of visualization through the Scanning Electron Microscope (SEM). The inputs were obtained from mining deposits, crushing diatomites, and marketing them as agricultural amendments, insecticides, or filter layers. The recognition of the species and the morphology of the frustules analyzed are shown in Figures 1-4.  
The scanning electron microscope is a Carl Zeiss Evo HD 15, with a LaB6 (lanthanum hexaboride) emitter, using Smart SEM software version 5.07. The X-ray energy dispersive spectroscopy (EDS) detector, an Oxford Instruments X-max 20, uses AZtec 3.0 SP2 software. The metallizer for the samples is a Quorum Q150R ES.  
The EDS tests were executed with the SEM. The multiple observations considered the following configuration: livetime (s): 30.0-181.9; process time: 2; Accelerating Voltage (kV): 15.0; Magnification: 1600X; Working Distance (mm): 8.3-8.8; Elevation (degrees): 35.0; Number Of Channels: 2048; Energy Range (keV): 20; Energy per Channel (eV): 10.0; Detector Type: X-Max; Window Type: SATW.  
The chemical composition of the frustules (presence of minerals or compounds) was studied by Energy Dispersive Spectrometry (EDS) and X-ray diffraction (XRD). From the former, peaks of Oxygen and Silica could be recognized in the three species. Other elements such as Aluminum, Sodium, and Carbon were identified, but in minimal concentrations. See Figure 2.  
From the XRD tests conducted on samples from three different sources, peaks matching silicon dioxide SiO\({}_{2}\) were detected. This description aligns with the characteristics of amorphous hydrated silica and pure biogenic opal. Please refer to Figure 3.  
The diffraction tests (XRD) were carried out with a Malvern-PANalytical model Empyrean 2012 brand equipment, with a Pixel 3D detector and a Cu source (\(\lambda\) = 1.541) at 45 kV and 40 mA. Goniometer: Omega/2 theta. Platform Configuration: The reflection Transmission Spinner is rotating at 4 rpm. The step was 0.03\({}^{\circ}\), and the time per step was 50 s. Identification was performed using High Score Plus software and the Rietveld method. Database: ICSD FIZ Karlsruhe 2012-1.  
Figure 1: Identification of species employing SEM. (**a–c**) Colombia (Boyaca)_Aulacoseira Granulata_Centric monospecies, cylindrical; (**d–f**) Mexico (Jalisco)_Cyclostephanos tholiformis_Centric monospecies, disc shape; (**g–i**) Peru (Ica)_Thalassionema nitzschioides_Elongated, symmetrical shapes. Colombian species Length (\(\upmu\)m): 5.19–38.66; Diameter (\(\upmu\)m): 4.04–23.97_Mexican species Diameter (\(\upmu\)m): 3.09–28.52_Pervvian species Width (\(\upmu\)m): 0.96–5.42.  
Figure 2: Mineralogical identification by EDS in frustules of different diatom species (**a**) Colombia_Aulacoseira Granulata; **(b)** Mexico_Cyclostephanos tholiformis; **(c)** Peru_Thalassiona nirzschioides.  
Figure 3: XRD characterization of frustules of different diatom species. (**a**) Colombia_Aulacoseira Granulata; (**b**) Mexico_Cyclostebanos tholiformis; (**c**) Peru_Thalassionema nitzschioides.