Iridium is a hard dense metal, that is the most corrosion resistant metal. This often means its used in spark plugs and in a huge number of alloys for strengthening or corrosion resistance. Though it’s rarity makes it difficult to obtain.
Scorpions aren’t rare but they are often quite hard to find, and their tails are hard and difficult to avoid if one is wanting to catch them. Most are not toxic, but will hurt considerably if they sting you. It’s tied to iridium as they are both hard to find.
Platinum is the “rich mans silver” often a substitute for white gold in some jewelry for purposes of hardness. It’s also used in electronic components, catalytic converters, thermometers, and chemotherapeutic agents. It can be toxic as a salt but not when pure.
Donkeys are known to be hard working, sure footed and somewhat grumpy animals that have been used as beasts of burden by humanity for centuries. Not to be confused with mules or hinny, which are interned with horses. They are tied with platinums as they are equally hard working and diverse.