When exposed to sunlight (UV radiation), the manganese undergoes a chemical change, shifting the glass from clear to various shades of amethyst or violet. 2. Archaeological Significance
Sun-colored amethyst refers to glass that has turned a purplish tint due to prolonged exposure to ultraviolet (UV) light. This phenomenon is not natural to the glass's original state but is a chemical reaction involving manganese oxide, which was used as a decolorizer in glass production between approximately . 1. Chemical Composition & Origin Colored Amethyst
Around the start of World War I, the supply of manganese (largely imported from Germany) was cut off. US manufacturers switched to selenium , which turns a straw or amber color when exposed to the sun, marking a distinct shift in the archaeological record. 3. Common Artifact Types Archaeologists frequently recover SCA in the form of: When exposed to sunlight (UV radiation), the manganese
When first produced, this glass appeared perfectly clear. This phenomenon is not natural to the glass's
This report examines glass, a specific type of historic artifact frequently used by archaeologists to date sites from the late 19th and early 20th centuries. Executive Summary
Manufacturers added manganese oxide to "mask" the natural green or aqua tint caused by iron impurities in the sand used for glassmaking.
SCA glass is a critical diagnostic tool for cultural resource assessments and archaeological surveys.