A mineral scale containing calcium carbonate that can form as hard water changes chemistry, is heated, or evaporates.
GlassRenu email archive — publication credit pending
Meaning and boundaries
Not every white deposit is calcium carbonate, and a calcium-carbonate component does not exclude magnesium, silica, iron, organic matter, or other constituents.
Why it matters in glass restoration
Chemical identification matters because removal response and compatibility cannot be inferred reliably from a white or chalky appearance alone.