###### Abstract  
Minerals have played a fundamental part in prebiotic chemistry on Earth, catalyzing the synthesis of inorganic and even organic molecules, including macromolecules such as RNA or DNA. Minerals based on silica are some of the first inorganics to be found in very ancient mineral fossils. These minerals or even volcanic glasses rich in silica, such as obsidians (a naturally volcanic glass, which is in fact an igneous rock), play an important role as supporting materials for obtaining the silico-carbonates of alkaline earth metals (usually called biomorphs). This is because, in most radiolarians, diatoms, and foraminifera, their external shells are made up of silica (SiO\({}_{2}\)). However, it has yet to be evaluated whether the silica contained in the minerals present in the prebiotic era of the Earth interacted with the chemical elements that were also present during that era. To evaluate whether obsidian participated in the formation of the first inorganic structures of pioneering organisms, this study aimed to synthesize calcium and barium biomorphs on igneous rock and to show that dissolved organic and inorganic molecules might have interacted with the molecules of obsidian, producing a plethora of shapes that mimicked the cherts of the Precambrian. biomorphs; obsidian; silica-carbonate alkaline Earth metals +
Footnote †: journal: Applied sciences  
0000-0001-8000-80000-80000-800000-80000-800000-800000-800000-800000-800000-800000-800000-800000-8000000-8000000-8000000-80000000-8 nucleus of the planet [3]. It is due to this process that there was the evolution of the minerals, as well as the volcanic glasses, formed when lava was extruded from volcanos and formed igneous rock; the interaction between the chemical elements that make up each mineral contributed to the origin of life [1; 2; 3; 4; 5]. It is important to mention that each type of mineral has a characteristic crystal structure and a specific chemical composition that results from the combination of the elements present in the Earth's crust. For example, oxygen has been described as the most abundant element in characterized minerals and igneous rocks, followed by silicon [5]. A high percentage of oxides and minerals rich in silica (the majority of which are called silicates) have been found in the Earth's crust, in which elements such as aluminum, iron, calcium, magnesium, sodium, and potassium are combined. Silica minerals were among the first minerals to be formed and can be found in very ancient rock fossils (pseudomorphs of silica have also been found in Precambrian cyanobacteria) [6]. As such, silicates make up approximately 90% of the Earth's crust. Some of the more common silica minerals include feldspar, micas, pyroxenes, amphiboles, and olivines, among others. Silica is also found in nature in seven different polymorphs, namely, quartz, cristobalite, tridymite, coesite, stishovite, and amorphous polymorphs like lechatelierite and opal [7; 8]. Obsidian is a volcanic glass rich in silica, oxygen, aluminum, sodium, and potassium. Therefore, it is a good candidate for emulating the minerals rich in silica [9; 10]. Obsidian has been described by some authors as similar to glass, due to the fact that it is the result of the rapid cooling of viscous volcanic lava rich in silicon, oxygen, aluminum, and potassium and, therefore, does not crystallize adequately. There are various types of obsidian, the most well known being rhyolitic obsidian (containing more than 66% silicon by weight), dacitic obsidian (containing between 52 and 66% silicon by weight), and tachylite (basaltic glass containing less than 52% silicon by weight) [9; 10]. Obsidian is generally black or gray in color, although other colors are also possible, depending on the composition and the formation circumstances [11]. The importance of analyzing the trace elements in obsidian is due to their unique chemical properties and to the fact that they have a greater variation in concentration with respect to the other elements [12; 13; 14].