A few kilometres from Thamrait, littering the desert sand are petrified cauliflower “stones” that crumbles under the weight of car tyres. They vary in size — some as small as marbles while the others can be as big as a football. While they are scattered in wanton abandon around the Thamrait area, exploring further towards the Empty Quarter yields more fields comprised of these fascinating rocks. It’s not the outside appearance however that gets people’s attention but what’s inside which depending on location and condition, the fascinating crystal can come in different colours and hues.
“Oman is a country I love. I used to live in the Muscat area in the 1980s and took frequent trips into the interior, where we would camp and explore the many wadis and mountains. We also made excursions through the Rimal Al Sharqiya. However, on these numerous trips we found a variety of fossils but never any geodes,” shared Liza Axford who recently explored Thamrait with her husband Steve.
“Geodes have fascinated me ever since I lived in Oman but I never got the chance to visit the area near Thamrait in which they are found,” she shared.
“During our recent holiday in Southern, Oman our excellent guide Alawi of Dhofar Delight Tours drove us to an area in the Empty Quarter. He got out of the vehicle and after a short inspection of the ground picked up what looked like a small, dirty cauliflower head,” she said.
“I instantly recognised it as a geode! After a few minutes of searching, we had found several of these amazing rocks. Some were lying exposed upon the sand while others were partially buried. There were many different sizes from about the size of a golf ball, to one, the largest I have ever seen, almost as big as a football! Some were broken revealing them to be hollow. Inside the spherical ball of rock, it was creamy and looked like droplets of frankincense. Fascinating!,” she added.
“If you find one, treasure it, as it is a unique gift from nature,” she said.
Liza understood that geodes are found throughout the world, mostly concentrated in deserts, volcanic ash beds, or regions containing limestone.
Some are created in the hollow areas of soil such as animal burrows or tree roots. They are also formed in the bubbles of volcanic rock. Over time, dissolved minerals seep into the hollow area and harden into an outer shell creating the geode. Some of the larger specimens can have taken a million years to grow.
Her readings and study also informed her that geodes vary in their structure — some having a crystalline-like structure that glistens in the light and the outside construction can vary from smooth to rough.
“I have found several in my travels but they have the same common feature in that they are ball shaped and hollow. Some have even been made into table lamps, which show off their amazing structure,” she said.
While it’s easy to mistake them as stones, geodes are more fascinating than their usually petrified cauliflower-forms.
In fact, according to the German University of Technology in Oman (GUtech) assistant professor André Pinto who specialises in Geochemistry, mineralogy and Earth Science, calling them ‘stones’ would be an incorrect classification.
“In geology, there are rocks and minerals. Never ever use the word ‘stone’ to describe geodes, which are crystal aggregates. Stones are a band,” he pointed out on a social media discussion.
While a common belief is that geodes may take some millions of years to form just like other crystals, Pinto said, “Take it from a mineralogist specialising in crystal growth… Kinetics of crystal growth can be quite fast in some systems, given the right conditions. For instance, you can grow large gypsum crystals in a few days. Some phosphates take hours. We are talking about sparingly soluble phases, not carbonates and silicates which are formed in volcanic and sedimentary conditions,” he said.
Because of the beautiful crystal inside geodes, it is believed that in Oman, they are some of the most trafficked geological heritage in Oman next to meteorites and fossils.
In 2016, prominent Omani geologist Dr Ali al Lazki has called for tough regulatory, security and penal action for smuggling geological artefacts saying that closer scrutiny should be made not only in airports but also at land borders to thwart the attempt of burglarising Oman’s geological treasures.
He has then called for “formulation of policies that not only advocate measures against the loot of meteorites, but also educate the general public about the national pride and value associated with these rocks” adding that “their theft deprives Oman and its scientific community of the opportunity to learn from these rocks and to share this knowledge with the rest of humanity.”