In spite of color being one of the physicochemical parameters most commonly used to characterize a rock, very limited studies have studied the correlation between the nature, chemical composition, and color of a rock. This study presents a new approach for quantitatively assessing the relationship between these three parameters for specific rocks (example of igneous and sedimentary rocks) collected from the High Atlas of Morocco. A spectrophotometer was used to measure the color of samples, and the measurements were expressed in CIE L*a*b* color system units then converted to Hex color codes. Whereas, the chemical composition of samples was carried out by X-ray fluorescence. The most abundant oxides in magmatic rock samples are SiO₂, Al₂O₃, Fe₂O₃, MgO, and CaO, while K₂O, Na₂O, TiO₂, and P₂O₅ are generally found in trace concentrations. Two categories of clays were studied, non-calcareous raw materials without carbonate contents (<4% CaO) and calcareous clays or marls (CaO > 10%). Phosphate samples are rich in phosphorus (4.4%-17.5%) and CaO (11.2%-42.7%) with relatively low contents of SiO₂ (28.5%-52.2%), Al₂O₃ (3.1%-17.5%), and Fe₂O₃ (1.1%-6.6%). Results show that the change in the content of these elements from one rock type to another may be indicative of rocks with particular characteristics that do have an impact on color. The main coloration agent of clays was iron, Fe²⁺, and Fe³⁺ ions can color clay minerals either red or green or in various shades of orange and brown. However, in marls and phosphates, the high concentration of carbonates inhibits this iron effect by affecting a* (red) and b* (yellow) color parameters, which leads to grayish materials. The same applies to magmatic rocks rich in Fe₂O₃ and CaO.

中文翻译：

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元素成分如何影响火成岩和沉积岩的颜色：摩洛哥高阿特拉斯岩石的案例

尽管颜色是最常用于表征岩石的物理化学参数之一，但非常有限的研究研究了岩石的性质、化学成分和颜色之间的相关性。本研究提出了一种新方法，用于定量评估从摩洛哥高地图集收集的特定岩石（火成岩和沉积岩示例）的这三个参数之间的关系。使用分光光度计测量样品的颜色，测量值以 CIE L*a*b* 颜色系统单位表示，然后转换为十六进制颜色代码。而样品的化学成分是通过 X 射线荧光进行的。岩浆岩样品中含量最多的氧化物是SiO ₂、Al ₂ O ₃、Fe ₂O ₃、MgO和CaO，而K ₂ O、Na ₂ O、TiO ₂和P ₂ O ₅通常以痕量浓度存在。研究了两类粘土，不含碳酸盐的非钙质原料（<4% CaO）和钙质粘土或泥灰岩（CaO > 10%）。磷酸盐样品富含磷 (4.4%-17.5%) 和 CaO (11.2%-42.7%)，SiO ₂ (28.5%-52.2%)、Al ₂ O ₃ (3.1%-17.5%) 和铁₂ O ₃(1.1%-6.6%)。结果表明，这些元素的含量从一种岩石类型到另一种岩石类型的变化可能表明具有特定特征的岩石确实会对颜色产生影响。粘土的主要着色剂是铁、Fe ²⁺，Fe ³⁺离子可以使粘土矿物呈红色或绿色或橙色和棕色的各种色调。然而，在泥灰和磷酸盐中，高浓度的碳酸盐通过影响 a*（红色）和 b*（黄色）颜色参数来抑制这种铁效应，从而导致材料呈灰色。这同样适用于富含Fe ₂ O ₃和CaO的岩浆岩。