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:
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
When first produced, this glass appeared perfectly clear.
The purplish hue is the result of a specific manufacturing process:
SCA glass is a critical diagnostic tool for cultural resource assessments and archaeological surveys.
Because manganese was the primary decolorizer used specifically from 1890 to 1920 , the presence of SCA shards helps researchers pinpoint the age of a historical site.
Found in the ruins of late-Victorian and early-20th-century structures.
💡 If you find purple glass in a historical context, it likely dates to the turn of the 20th century and was originally crystal clear before being "sun-colored" by decades of exposure. APPENDIX E: CULTURAL RESOURCE ASSESSMENT
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:
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
When first produced, this glass appeared perfectly clear.
The purplish hue is the result of a specific manufacturing process:
SCA glass is a critical diagnostic tool for cultural resource assessments and archaeological surveys.
Because manganese was the primary decolorizer used specifically from 1890 to 1920 , the presence of SCA shards helps researchers pinpoint the age of a historical site.
Found in the ruins of late-Victorian and early-20th-century structures.
💡 If you find purple glass in a historical context, it likely dates to the turn of the 20th century and was originally crystal clear before being "sun-colored" by decades of exposure. APPENDIX E: CULTURAL RESOURCE ASSESSMENT