Gold

I remember, in class Xth, our science teacher gave us a detailed note on properties of Gold and its usefulness and its reason for being expensive.

What i remember a bit of scientific information from it about Gold which make it expensive is (although i dont remember the exact scientific terms) -

- Gold is referred to as a "noble" metal because it does not oxidize under normal conditions. 

- Its less harmfull for human body as compared to other metals, hence Its used in medical field (specially by dentists)

- Gold is a chemical element so it can only be found, not manufactured.

- It is easy to store cheaply for long periods

- It is also known for its rarity, density, softness, and its very good electrical conductivity

-It is extremely rare, and its extraction cost is very high.

- Because of its rarity gold signifies scarceness, which is what occasionally makes it useful as money

- Gold is difficult to counterfeit. Any one accustomed to handle gold money can detect a spurious gold coin at a single glance.

- It can be easily deformed  and is easily divisible.

 - Its least harmful for our environment as its not easily decayable and dont easily react with other metals/acids etc.

- Traditionally/Historically also gold was given immense importance as compared to other metals.

Regarding you second question why world runs behind gold, I think a girl can give you a better answer!!!

very good information but the last point is good that a women can give better regarding gold.