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Diamonds might be forever, but are they old? The jeweler at my local jewelry store would probably tell me the diamond in my wedding band has been around for hundreds of millions of years. And the idea is romantic, isn’t it? To think this piece of rock (because I do love rocks) was sitting there, waiting just for me, for more days than I can count, so I could wear it on my finger as a shiny symbol of my commitment to my husband. Definitely romantic, but is it true?
My diamond certainly wasn’t formed in the year before my husband bought it, but there are a couple of problems with thinking diamonds are millions of years old. Recently, deep inside a kimberlite pipe (the volcanic rock which is the source of most of the world’s diamonds) a rare discovery was made. Fresh, unpetrified, wood was found 1,000 feet down, entombed in the kimberlite. This wood probably fell into the debris along the margins of the kimberlite pipe, and as the eruption slowed it became emplaced within the rock. But it’s not fossilized. It’s the same as any wood that you would use in a bonfire. Which begs the question, how could this wood stay unpetrified for hundreds of millions of years? How would this wood stay woody (also a fun tongue twister)? If the wood isn’t old, the diamonds shouldn’t be either.
Scientists have also demonstrated that it’s possible to create diamonds in the laboratory in mere hours using the correct temperature and pressure. So, why do some people think it would take millions of years in nature? Perhaps because it fits with a particular world view regarding the age of the earth.
Another clue about the age of diamonds comes from the radioisotope Carbon-14. This carbon isotope has been found within diamonds. Carbon-14 has a half-life of approximately 5,370 years. So, half of the radioisotope will revert back to non-radioactive material in 5,370 years. Which means that within 100 thousand (not million) years, the level of Carbon-14 in the rock would have fallen below detection levels. Since scientists have detected Carbon-14 in diamonds, we know they must be younger than 100 thousand years.
Diamonds might last forever, but it’s not likely they are as old as the guy at the jewelry store claims. No problem for me. I still love my shiny proof of commitment to my husband. And I wouldn’t discourage him from buying me some more for my ears.
What do you think? Should scientists claim an age for rocks when there could be contrary evidence? Can we ever prove the age of something without knowing for sure how it formed?
Reference: O’Brien, Jonathan. (2014). Diamonds, Are they really all that old? Creation, 36 (2), 22.