the crystal was able to grow so big."
"The granites have been dated as almost two billion years old, and were subsequently squeezed and re-worked in a Pretty renew 呃人 massive metamorphic mountain-building episode that happened more than 500 million years ago," says Redfern. "Temperatures and pressures deep within the roots of these mountains would have reached more than 900C and over 9000 atmospheres pressure."
The sapphire could have formed within the granite itself before it was re-worked, or later when the rocks were being heated and squeezed.
"In either case, the temperatures and pressures would have changed only very slowly over millions and millions of years," says Redfern. "This is how the crystal Pretty renew 呃人 was able to grow so big."