The onyx in Soledade, a gem mine in the south of Brazil, is a replica of a blue cartoon character with big eyes called the Cookie Monster.
After the owner of the stone worker and mineral collector in California, Mike Bowers, shared a photo taken on the social network Facebook on January 16, the onyx block immediately caused a fever. Bowers said he didn’t know Cookie Monster was so popular. The agate block was brought to Bowers in November 2020 through Brazilian gemologist Lucas Fassari. Prior to that, Fassari purchased a series of onyx from the Soledade mine. Bowers immediately bought the Biscuit Monster stone, but due to Covid-19 infection, more than a month later he posted the photo.
The Onyx Block and the Biscuit Monster from the Sesame Street cartoon. (Photo: Kennedy News).
Agate is a form of quartz, a silicon dioxide crystal, that grows inside fissures in volcanic rock. These cavities are formed by air bubbles in hot lava. Over time, the lava cools, and silicon dioxide-infused water seeps through the cavity. As the water evaporates, silicon dioxide collects in the cavity walls, creating layers of colorful crystals. That color is a result of chemical impurities in the silicon dioxide and the spacing between the crystals.
Some blocks of agate completely fill the crater, but some rock samples have a small gap, surrounded by sparkling quartz crystals towards the center. In the case of Cookie Monster agate, the gaps happen to look like cartoon character’s eyes and smiling mouth. That is the feature that makes the stone so unique.
Another special feature of the Cookie Monster agate is that the faces appear on both sides of the rock, according to Bowers. Often, the gaps don’t line up neatly enough to produce the same image on the other side. Currently, Bowers is holding the gem block. He will probably donate it to a museum or resell it to a high-end collector in the future.