Hardshell consists of hydrophobic and lightweight polypropylene (PP). Exhibits high stiffness, very high impact properties at room and sub-zero temperatures, good dimensional stability, excellent creep and deforming resistance. Was used for crates, panels and profiles, blow molded bottles, containers, corrugated sheets, conduit pipes, fittings for electrical distribution and fibres for clothing.

Due to their low density some synthetic stones show a particularly high physical buoyancy. Thus, they mostly occur on the surface of the sea water like a new type of floating rocks. However, in this position they are not only exposed to the direct impacts of sun and wind. But as part of the existing cycles of the ocean's surface currents they are also able to cover large spatial distances.

Pollution Type:	Marine litter
Material Origin:	Burned or melted plastic that was exposed to marine weather conditions
Age:	Partly can be determined based on specific additives (e.g. lead and cadmium) which were often used in the 1950s but became widely regulated in the 1960s
Shape:	Stone-like appearance that ranges from angular plastiglomerates to more weathered-rounded clasts
Colour:	Often exhibits a single and neutral colour (black-charcoal-grey, off-white or brown) with occasional hues of green, blue, pink or yellow
Texture:	Regular surface features include cracks and fractures as well as pits and cavities
Size:	Common objects range between20 mm (clasts) and 5 mm (fragments)
Occur- rence:	Shows a distinctly geogenic appearance in certain coastal areas and can get further distributed by oceanic currents
Buoy- ancy:	Objects with a polyethylene or polypropylene matrix demonstrate a positive buoyancy
Toxic Potential:	Possible hazardous substances include bromine (Br), cadmium (Cd), chromium (Cr) and lead (Pb) as well as several polymeric additives
Bioavail- ability:	Partly used as habitat by tubeworms (Spirobranchus triqueter) and algeas

The water was nearly always covered in oil, plastic and toxic foam, and it bubbled like a deadly stew. Sometimes rats floated by, their corpses so bloated they were practically the size of dogs. It was disturbing, but it was also just one of the realities of the city. For more than a century, the Riverfront had been prime real estate for various manufacturing companies. Everyone knew it was polluted, but pollution meant industry was thriving, the economy was booming, and everyone had jobs.