Given a passage and a query based on the passage, generate an unambiguous, concise and simple answer to the query from information in the passage. Note that the answer may not be present in exact form.
Q: Diamonds can form at depths as shallow as 150 kilometers beneath the continental crust, while beneath oceans they need depths of at least 200 kilometers, as shown by the diamond boundary on the cross-section. Diamonds are formed as an allotrope of the element carbon, at depths greater than 90 miles. The pressure and heat at this depth is critical to the formation of the diamonds th at are mined at the surface today. At crustal pressures, the stable form of carbon is the allotrope graphite. Diamonds are formed as an allotrope of the element carbon, at depths greater than 90 miles. The pressure and heat at this depth was critical to the formation of the diamonds that are mined at the surface today. At crustal pressures, the stable form of carbon is the allotrope graphite. How Diamonds Are Formed. If you're out there looking for the best diamond for your money, then please contact us and let us know your budget and what you're looking for. We'll sift through thousands of diamonds online and send you suggested stones to choose from that fit your needs the best. Last Updated: September 5, 2017 Diamonds are formed as an allotrope of the element carbon, at depths greater than 90 miles. The pressure and heat at this depth is critical to the formation of the diamonds that are mined at the surface today. At crustal pressures, the stable form of carbon is the allotrope graphite. Diamonds can form in most of Earth's interior but not near its surface, where graphite is the stable form of carbon. Indeed, diamonds only survive at Earth's surface because great heat is required to break down the diamond structure. Diamond is not formed from metamorphosed coal, and most diamonds discovered on the surface in mining operations are at least one billion years old; some may be two or three times that age. Diamond can also be formed from the pressures of high speed impacts of meteors with the Earth, but these are more of scientific interest, having no economic usefulness due to their small size and dispersion. How Diamonds Are Formed If you're out there looking for the best diamond for your money, then please contact us and let us know your budget and what you're looking for. We'll sift through thousands of diamonds online and send you suggested stones to choose from that fit your needs the best. Experiments and the high density of diamonds tell us that they crystallize at very high pressures. In nature this means that diamonds are created by geologic processes at great depth within Earth, generally more than 150 kilometers down, in a region beneath the crust known as the mantle. Other processes, explored later in this exhibition, bring diamonds to where people can find them. How are diamonds formed and where are they mined? Diamonds form about 100 miles (161 km) below the Earth's surface, in the molten rock of the Earth's mantle, which provides the right amounts of pressure and heat to transform carbon into diamond. Query: how does a diamond formed
A:
Diamonds are formed as an allotrope of the element carbon, at depths greater than 90 miles. The pressure and heat at this depth is critical to the formation of the diamonds that are mined at the surface today.