Which is the hardest metal found in nature?

The correct answer is Tungsten.

Important Points 

• The hardness of the mineral is defined on Moh's scale of hardness. On this scale, a mineral is rated between 1-10 on the basis of its strength.
• It is used to rate the hardness of a variety of substances and elements, not only metals. The softest materials it rates are assigned a rating of 1; the hardest earn a rating of 10.​ 

Key Points

The Moh's scale of different minerals is shown below.

• Tungsten is the hardest metal. ∴ Option 4 is correct.
• Platinum is a less hard metal. That's why it is used in Jewellery. It can make intricate designs. It is highly ductile.
• The name Tungsten originates from the Swedish name tungsten meaning heavy stone.
• Hardness is the ability to scratch making a dent on the surface of the metal. It is just a number measured using (Rockwell, Brinell, Vickers test)  Of which Brinell is most accurate.
• Gold: 25 Mpa
• Platinum: 40 Mpa
• Tungsten: 310 Mpa
• Iron: 150  Mpa
• Diamond: 10000 Mpa (Non-metal)
• It is a chemical element with atomic number 74 that has the highest tensile strength of all the metals present in the world. Its symbol is  "W"
• When combined with carbon, tungsten becomes stronger and even more durable. Tungsten carbide is the end product of mixing tungsten with carbon. Tungsten carbide is 4 times stronger than platinum with a hardness rating of 9 on the Mohs scale, softer only than diamond.
• From the above, 310 > 40, So, Tungsten is harder than Platinum.

Additional Information 

• The Youngs Modulus value of Tungsten is 34.48 × 1010 Pa and 
• The Youngs Modulus value of Platinum is 14.48 × 1010 Pa