Iron sulfide, or pyrite, is a mineral with a very distinct appearance. It's often referred to as "fool's gold" because it can look quite like gold in its raw form. Here's what you need to know about its look:

* Color: Pyrite has a bright, brassy yellow color, very similar to gold. However, it can have a greenish or brownish tinge depending on impurities.

* Luster: It has a metallic luster, meaning it reflects light like a metal.

* Crystal Form: Pyrite often forms cubical crystals with striations (lines) on their faces. It can also occur in other forms like octahedrons, dodecahedrons, and even massive, irregular shapes.

* Streak: The streak (the color of the mineral when rubbed on a streak plate) of pyrite is black to greenish-black. This is a key difference from gold, which leaves a golden streak.

Important Note: While pyrite is very common, it's important to note that it is not gold. It is much softer than gold and can be easily scratched with a knife.