DEL MAR (CBS) — An 18-carat diamond = $1 million. The cost of gas from Los Angeles to Del Mar = maybe $50. Posting a photo of yourself on Facebook wearing a diamond nearly the size of a quarter? Priceless.

One Del Mar jewelry store is letting members of the public try on its huge diamond for free — all you have to pay is the cost of gas from LA.

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The massive diamond, known as the triple crown diamond, is mounted on a simple black necklace. The face of the rock is just a bit smaller than a quarter.

There are larger diamonds out there, but most of them are museum pieces or in the private collection of a wealthy aristocrat.

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“For consumers, you’ll have a once in a lifetime opportunity to actually see it, touch it and try it on,” gemologist Natasha Digius-Mahdavi said.

The triple crown is rare not only for its size, but its quality, cut and clarity. Digius-Mahdavi says this is the type of diamond that is found literally once every hundred years and that there are probably less than 50 stones in the world that are of this size and clarity.

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The estimated value of the triple crown diamond is $1 million.