Antropogenic (Man-made)
Blue Slag Glass
Amorphous Silica (Byproduct of smelting)
Hardness: 5.5-6.5 (Mohs), Color: Vibrant blue, Luster: Vitreous to glassy, Crystal Structure: Amorphous (non-crystalline), Cleavage: None (conchoidal fracture), Specific Gravity: ~2.4-2.8
- Hardness
- 5
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Physical properties
Hardness: 5.5-6.5 (Mohs), Color: Vibrant blue, Luster: Vitreous to glassy, Crystal Structure: Amorphous (non-crystalline), Cleavage: None (conchoidal fracture), Specific Gravity: ~2.4-2.8
Formation & geological history
Formed as a byproduct of historical iron or glass smelting processes. The blue color often comes from cobalt or copper additives. Usually dates from the Industrial Revolution (19th to early 20th century).
Uses & applications
Historical waste product now used for lapidary work, decorative landscaping, aquarium stones, and wire-wrapped jewelry.
Geological facts
Also known as 'Leland Blue' or 'Sieber Agate' depending on the region found. It was often dumped into lakes or rivers near smelting factories, where it becomes rounded by water over decades.
Field identification & locations
Look for a glassy texture and air bubbles (vacuoles), which distinguish it from natural minerals like Lapis Lazuli. Commonly found in former industrial regions of Michigan, Pennsylvania, and Germany.
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N/A - Non-Geological Item
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