Diamond -

Because diamonds are the hardest known natural material (10 on the Mohs scale), they can only be polished using another diamond. The process of transforming a rough stone into a gem involves five steps: planning, cleaving/sawing, bruting, polishing, and final inspection. The 4 Cs of Quality

Volcanic eruptions transport these diamonds to the surface through kimberlite and lamproite pipes. DIAMOND

The value of a diamond is largely determined by the GIA grading system's 4 Cs: The weight of the diamond. Because diamonds are the hardest known natural material

Most natural diamonds are between 1 and 3 billion years old. The value of a diamond is largely determined

Diamonds are created about 150-200 km beneath the Earth's surface, where extreme pressure and high temperatures force carbon atoms into a stable crystal lattice.

What to look for in a certificate (like GIA) How to Make a Real Diamond - (Not Clickbait)