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:
💡 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 Colored Amethyst
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 Around the start of World War I, the
When first produced, this glass appeared perfectly clear. Archaeological Significance When first produced