Which statement best describes the characteristics of diamond?

The statement that diamond is formed from carbon under high pressure accurately reflects the geological process that leads to the creation of diamonds. Diamonds are made entirely of carbon atoms arranged in a specific crystal structure called a diamond cubic lattice. This unique arrangement contributes to their hardness and durability. The formation occurs deep within the Earth's mantle, typically at depths of around 150 to 200 kilometers, where high temperatures and pressures allow carbon to crystallize into diamonds over millions of years.

This characteristic is what sets diamonds apart in terms of their physical properties, such as their renowned hardness, making them the hardest natural material known. The other statements do not accurately represent the nature of diamonds: they are not soft or easily scratched, nor are they porous and lightweight; diamonds are actually very dense and solid. Additionally, diamonds are not classified as fossil fuels, which are organic materials derived from decayed organisms.