We no longer use commercially use crystals in radio tuning. We've fully converted to solid state tuners. When we did use crystals a few different kids were used. We used galena, molybdenite, iron pyrite, Carborundum , silicium ...and "Cristadyne." (sometimes spelled Crystadyne or Crystaldyne) Simply put it was the fairly rare crystal zincite aka ZnO4.
It was Karl Braun who in 1874 discovered that crystals had rectifying properties. But even after radio stations were popping up across America, the mechanism behind rectification was totally unknown. In the U.S. we were moving on to vacuum tubes, without every having fully understood the physics behind the crystal sets we'd been using for decades. the prevailing theory was that it was an unknown thermal effect. The real progress on this front happened in Russia. Vacuum tubes were very expensive, and in Russia the push was on to jump to a solid state tuner. Oleg Losev was self-taught and began by investigating fluorescence in the carborundum-based LEDs invented by Henry Round.
Fluorescence is the emission of light, not normally of much interest in radio. But Oleg in his obsession wrote dozens of papers and realized in his scrutiny that the fluorescence was a quantum effect. Therein he found a correlation between short wavelength cutoff energy and applied voltage. Eureka. He went on to find that with zincite diodes he could achieve negative resistance. His experiments with voltage biases refined reception. He gained amplification, he designed regenerative and superheterodyne receivers, and eventually transmitters. (before Armstrong) These were all fully solid state units. No tubes. He published his findings in an article an article, for the Russian trade mag Telegrafiya i Telefoniya bez provodov (Wireless Telegraphy and Telephony) in 1927. But at the time the revolutionary communist government of the USSR was disinterested. he toiled alone and in vain. The USSR also didn't support the free flow of information as we do. So the notion of small rural hamlets making their own radios, and worse-yet TRANSMITTERS, was unwelcome. The information was even less likely to travel to the U.S. due to poor post WWII relations. We had to rediscover it all on our own. Oleg Losev starved to death in 1942 during the siege of Leningrad.