Short answers, pulled from the story.
Diamonds were first recognized and mined in India, where significant alluvial deposits lay along the rivers Penner, Krishna, and Godavari. India has known diamonds for at least 3,000 years, and possibly as long as 6,000 years. India led global diamond production from approximately the 9th century BC until the mid-18th century AD.
Diamond's hardness comes from its crystal structure, in which every carbon atom bonds to four neighbors in a rigid tetrahedral arrangement. Diamond holds the greatest number of atoms per unit volume of any known substance. This sp3 bonding geometry makes it both the hardest natural material and the least compressible.
Colors in diamond originate from lattice defects and impurities. Nitrogen causes yellow and brown hues; boron causes blue; radiation exposure from alpha particles causes green; and plastic deformation of the crystal lattice is responsible for some pink and red stones. Pure diamond with no impurities appears colorless.
Most gem-quality diamonds form at depths of 150-250 kilometers in the Earth's mantle, at pressures around 4.5 gigapascals and temperatures near 950 degrees Celsius. A smaller group forms at depths of 330-660 kilometers in the mantle transition zone, and another proportion originates at depths between 660 and 800 kilometers in the lower mantle.
Synthetic diamonds are produced by two main methods: high-pressure high-temperature (HPHT) processing, which mimics the natural conditions inside the Earth, and chemical vapor deposition (CVD), which grows diamond from a mixture of hydrocarbon gases, typically methane and hydrogen, split into reactive radicals in a plasma chamber. As of 2014, around 4.5 billion carats of synthetic diamonds were produced per year, with 90% made in China.
Conflict diamonds, also called blood diamonds, are stones mined by armed groups in politically unstable countries to fund military operations. The Kimberley Process was introduced in 2002 by the United Nations and the diamond industry to prevent conflict diamonds from entering legitimate supply chains. According to the International Diamond Manufacturers Association, conflict diamonds still represent 2-3% of all diamonds traded.