mineraloid / anthropogenic material
Cobalt Blue Sea Glass
Amorphous Silica Glass (SiO2 + CoO)
Hardness: 5.5-6 (Mohs); Color: Deep cobalt blue; Luster: Frosted/Vitreous; Structure: Amorphous (non-crystalline); Fracture: Conchoidal; Specific Gravity: 2.2-2.5
- Hardness
- 5
- Color
- Deep cobalt blue
- Luster
- Frosted/Vitreous
Identified More mineraloid / anthropogenic material →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 5.5-6 (Mohs); Color: Deep cobalt blue; Luster: Frosted/Vitreous; Structure: Amorphous (non-crystalline); Fracture: Conchoidal; Specific Gravity: 2.2-2.5
Formation & geological history
Formed from discarded glass manufactured predominantly in the 19th and early 20th centuries. It achieves its smooth, frosted texture through decades of hydration and mechanical weathering from ocean waves and sand.
Uses & applications
Used primarily in artisanal jewelry, mosaic art, and as a decorative collector's item due to its rarity compared to other colors.
Geological facts
Cobalt blue glass is much rarer than green or brown glass because it mainly originated from vintage medicine bottles (like Noxzema or Bromo-Seltzer) and perfume vials. It takes approx. 20-50 years for a fragment to become high-quality sea glass.
Field identification & locations
Identify by its 'frosted' surface and 'C'-shaped hydration marks. Found along shoreline tide lines, specifically in rocky or high-energy beach environments globally. Rare pieces have no sharp edges and appear 'sugary'.
More like this
Other mineraloid / anthropogenic material specimens
Slag (Industrial Glass)
Anthropogenic Amorphous Vitreous Silicate
mineraloid
Cobalt Blue Slag Glass
Amorphous Silicon Dioxide (anthropogenic) with Cobalt additives
mineraloid
Slag (Industrial Glass)
Artificial Vitreous Silicate
mineraloid (anthropogenic)
N/A - Image does not contain a rock or mineral
Anthropogenic textile material
Non-geological
Slag
Ferrous slag (by-product of iron smelting)
Mineraloid / Anthropogenic
Cullet (Slag Glass)
Amorphous Silica (SiO2) with various metal oxide colorants
mineraloid / anthropogenic