Finding Giant Selenite Crystals

Knowing How Selenite Crystals are Formed Explains their Size

Underground chamber at Mexico's Naica lead-silver-zinc mine contained selenite crystals up to 37.4 long. Photo Courtesy Wikimedia Commons

Giant selenite crystals were not on my mind as a dealer chairman for the Tucson Gem and Mineral Show Committee, but I soon got an offer to see these crystals that I couldn’t refuse.

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As the dealer chairman, I was responsible for choosing dealers to be in the arena section. I reviewed new applications from mineral dealers who applied for a space in the forthcoming show. One such dealer applicant had enclosed quite interesting photos of large selenite crystals with his application. I gave him a call and during our talk, he told me he had just returned from a cave in Mexico that had selenite crystals as big as trees! Selenite properties as a gypsum mineral make it easily identified and naturally, I wanted to visit the cave. We made a deal. I gave him a space at the show and he arranged an invitation to visit. Little did I know I was about to see the largest natural mineral crystals in the world, These crystals were later featured on a National Geographic TV show and written up in their magazine a couple of years after we wrote the first published article in Rock and Gem.

Benny Fenn walking among selenites in the Cave of Swords.

The Cave of Swords

A few weeks after the show, we met the dealer in Tucson and headed to Mexico. Carol and I were joined by our dealer friends Benny and Elva Fenn. We were familiar with what is mined in Mexico and we drove to the Naica silver mine, Durango, already well-known among collectors for its silver minerals and selenite crystals. The mine had been featured in National Geographic about a selenite cave named the Cave of Swords, much smaller than the crystals we wrote about in Rock and Gem. We did go into the Cave of Swords at the 400-foot level on a later visit to Naica.

The crystals jutting from the floor of the Cave of Swords were up to three feet long in nice sprays. The walls were completely covered by four to six-inch crystals so dense you could not see the rock walls. There were tens of thousands of these small selenites lining the cave opening from floor to ceiling and extending deep into the mountain.

In the early days of the Cave of Swords, crystals were collected by the company doctor and sold to help pay for the treatment of injured miners and for families who had lost someone in mine accidents.

The Big Crystal Cave

Once at the mine to see the big crystal cave, we climbed in a small haulage truck and drove into the mine where the temperature grew warmer as we descended. As we drove along the lowest tunnel, we passed maybe a dozen exposed open pockets of selenite crystals that would have been a thrill for any collector.

We did stop next to a short side tunnel and I could see a set of cement stairs at the base of a small opening in the tunnel wall. I headed for that opening and crawled in on my hands and knees on selenite crystals surrounded by free-standing huge selenite crystals jutting from the walls and ceiling as far as I could see. This was just a preview of what was to come. I was told this cave might be connected to the nearby big crystal cave. As far as I know, no one has explored this entire cave system to determine if the two caves are one huge complex. The intense heat and high humidity in both caves and the size of the crystals jutting up at all angles make it almost impossible to proceed and prove the theory, but it is likely.

Getting to the Big Crystals

We drove another 100 yards or so and came to a short side tunnel painted white and well-lit. On one wall was a huge locked steel door. Our escort had the key, but before he opened the door and allowed us into the cave, our guide explained we could not be in the cave alone. He had to be with us at all times. Then he opened the door and a blast of hot air hit me like a blast furnace door had been opened. The temperature in the tunnel where we parked was 90 degrees but that blast of cave air took your breath away. You had to force yourself to walk into that heat and try to breathe.

My wife Carol, who is a silver metal casting artist used to handling high heat, stood in the cave doorway and simply said, “I’ve seen enough!” and backed out of the smothering heat.

An overall shot of large, tangled selenite crystals.

Giant Crystals

The miner stepped into the cave and I followed. I broke out in a sweat and gradually made my breathing more normal. In seconds I was wet from head to toe from sweat. My camera instantly fogged up. I was stunned by my surroundings!

Giant tree-like selenite crystals about four feet in diameter extended from the cave floor to the ceiling about 40 to 50 feet above us. The crystals looked like a forest of trees that had been blasted and uprooted by a hurricane. They were tilted in every direction, an amazing tangle of growth. Some crystals had fallen from their sheer weight since selenite does have perfect cleavage. You could sit astride fallen crystals as if riding a horse.

Bob crawling into the first of two giant selenite crystal caves.

Between where the crystals touched the ceiling were huge rosettes of selenite crystal groups hanging from the ceiling like chandeliers. I was in the cave for maybe five minutes and I had to bail out and enjoy the cooler tunnel outside. Others in the group were having the same problem. We would walk in and look around for a few minutes and get out. After several visits to the cave, I was able to stay for as long as 10 minutes at a time. Later we learned the cave temperature was a tough 140 degrees with humidity over 90 percent.

We had been at the cave off and on for over an hour and the miner who had gone in ahead of me had stayed in the entire time. When he walked out he looked like he had just stepped out of a shower. All his clothing was soaked. But he was game and we did another round of visiting until we had to leave.

I felt sorry for the guide who was required to go through that hot ordeal. Benny and I each put up $100 and Benny, who is bi-lingual, gave it to the miner who immediately took out a card, wrote a phone number on it, and said to Benny, “You want to go in the cave again, call me, not the office!” Needless to say, Benny and I accepted his suggestion and we visited the cave twice more before the company finally closed the cave so only scientists could visit it.

The Fate of the Crystals

Studies have shown the cave is above the Naica fault. Below the fault is a hot magma chamber. Estimates suggest the crystals took a million years to form first anhydrite crystals then reformed into selenite.

Unfortunately, mining at Naica has stopped which means the pumps that keep the water level down have been stopped. The water level will slowly rise and the cave will eventually flood above the 2500-foot level as it seeks its natural level. The day may come when the selenite crystals will dissolve back into solution. I’m just grateful I was able to spend time with those crystal monsters and share the experience.

This story about finding giant selenite crystals previously appeared in Rock & Gem magazine. Click here to subscribe! Story by Bob Jones.


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