All that glitters is not gold, and might not be good

 

You know what glitter is, right? That flaky shiny stuff kids can paint with, and which sometimes women put on their faces and eyebrows and such to look pretty and shiny and flashy? 

Like this, for example:

Well, if glitter gets into the ocean, apparently it can act as a crystallization site for the formation of calcium carbonate (CaCO3, where that "3" should be a subscript). This article talks about that, but it doesn't really identify a specific concern, just that it might be a problem.

Glitter Can Disrupt Marine Biomineralisation

Microplastics from PET-based glitter could have a negative long-term impact on marine ecosystems.

"The study mimicked seawater conditions and investigated six different types of PET glitter to determine how their surface properties influence the formation of Ca-Mg carbonate minerals. Using advanced analytical techniques, including scanning electron microscopy and infrared spectroscopy, the researchers found that glitter microplastics provide sites for CaCO3 crystallisation, accelerating mineral formation and potentially altering skeletal structures in marine organisms."

Well, I guess that's not good, but I don't see what kind of not good it is.

There is more.

"The researchers discovered that PET-based glitter microplastics can actively promote the crystallisation of calcium carbonate (CaCO3) minerals in seawater. Their experiments revealed that the surface properties of these microplastics, particularly their irregular textures and functional chemical groups, create favourable sites for mineral crystallisation. This means that when PET glitter is present in seawater, calcium carbonate forms more readily on its surface, potentially influencing the natural biomineralisation processes of marine organisms that rely on CaCO3 to build their shells and skeletons."

This is what I don't understand (and I need to read the paper, which is referenced below). If the glitter is causing CaCO3 formation in seawater, how does it affect biomineralization, which happens in association with an organism?  I.e., they make their CaCO3 out of calcium and carbonate ions, not out of solid CaCO3. 

I guess I better read the paper.

Reference: Zubovic KP, Horvath A, Brien DM, et al. Crystallisation of CaCO3 polymorphs induced by layered PET-based microplastic particles. Environ Sci Eur. 2025;37(1):52. doi: 10.1186/s12302-025-01090-0.

So, the whole paper is accessible, but to make things quick, there are Conclusions at the beginning. This helps explain some of the concerns.

"PET [Polyethylene terephthalate] uniquely influences surface CaCO3 nucleation compared to other microplastics. Unlike polystyrene or polyethylene, which require organic coatings for encapsulation, PET actively promotes crystallisation via ester (–COO–) and hydroxyl (–OH) groups that facilitate Ca2+ adsorption, creating local supersaturation zones. Surface defects further concentrate ions, accelerating mineral growth. Crystallisation in confined PET features enhances fragmentation, increasing micro- and nanoplastic release. The strong attachment of CaCO3 phases to PET may affect biomineralisation in marine organisms, impacting shell formation and skeletal integrity. Additionally, PET degradation through crystallisation-driven fragmentation raises concerns about increased microplastic bioavailability and long-term environmental pollution."

So I'd have to say, the less that glitters the better, at least in the ocean.