The composition of pebbles mainly includes the following substances:
Main ingredients
Silicon dioxide (SiO₂): It is the main component and is the basic chemical component of pebbles. Its colloidal form (such as silica colloidal chalcedony) can present a yellow translucent appearance.
Minor elements and compounds
Iron oxide (Fe₂O₃): It affects the color (such as vermilion).
Trace metal elements: including manganese (Mn), copper (Cu), aluminum (Al), magnesium (Mg), etc., which form different color systems after dissolving into silica hydrothermal fluids (such as blue from copper and purple from manganese).
Relationship between color system and pigment
Differences in element types and contents cause pebbles to present various colors such as black, white, yellow, red, dark green, and blue-gray.