Should I put the tiny fountain pen Ink Cartridge in the bin or the recycle Bin? Great question, and shows you are really the caring sort of person to know, that not all plastics are recyclable.
Recycling Stamps
Stamped on the product, usually on the base one should find the arrowed recycle symbol triangle with a number in side. This number refers to the type of plastic, and more specifically the molecule make up of the plastic. At a molecular level, certain molecules do not mix with other molecules and therefore cannot be added in the recycling process. Hence the need for some plastics to be separated from others. Read on to learn the most common Recycling Codes and then answer the question from the picture above
No Recycling Stamp? You cannot recycle and should put it in the bin
What can you recycle from the fountain pen ink cartridge?
The featured image of this post is a picture of a Parker Ink Cartridge and its box. Looking all over the cartridge I can find no mini stamp. So no stamp means no to recycling and you should put the fountain ink cartridge in the bin
The box however is a different matter, looking up code 21 in the chart below, it is indeed listed as a cardboard that should be recylced.
Recycling ink cartridge Summary:
Most Fountain Pen Ink Cartridges are unlikely to be recyclable but the packaging it comes in most likely will be.
Thanks for reading and taking care of planet Earth – there is only one planet Earth!
Recycling Codes gallery found on Products

PETE – Polyethylene terephthalate or sometimes written as Poly(ethylene terephthalate). In textile format, it is also known as polyester. In bottle form for instance water bottles, cooking oil bottles, and medicine containers.

Polyvinyl Chloride (PVC or Vinyl) thermoplastic polymer widely used in building and construction industry

You will know it if you see it, Tupperware, plastic caps, drink bottles, yoghurt tubs

Non-Corrugated fibreboard – cereal boxes, chocolate boxes etc

HDPE – High-density Polyethylene is one of the worlds most popular plastics. Heavy duty membranes to bags, shampoo containers, toys etc.

Common plastic for wrapping things, sandwich bags, grocery bags

The plastic that cracks, breaks and crumbles. Polystyrene cups, coffee cups, insulation. Naturally transparent.

A Category of other for less commonly used plastics, that can utilise combinations 1 through to 6