During a specimen-gathering mission on planet Alpha 177, a transporter malfunction creates an evil duplicate of Captain Kirk. Apparently, the transporter malfunction is caused by interference of the transporter technique with a magnetic, yellow ore found on the planet’s surface. The mineral is not identified in the episode but seems to possess some alien properties.
In many episodes, the crew of the Enterprise visits mining colonies or is on a mission to search for valuable minerals and crystals. There exists even a geological tricorder for prospecting resources, designed for analyzing rock samples and comparing them to the records memorized in the mineralogical database of the federation. By convention, the names of terrestrial minerals (a crystalline combination of one or various elements) end with the suffix "-ite", the denominations of elements with the suffix "- ium", "-um", "-on", "-gen" or "-ine". Unfortunately it seems that this nomenclature is not always applied with the necessary scientific accuracy in the 23th century. But to be fair, many of the minerals are unknown to the present day. And that's accurate, as there are indeed elements found only in stars and outer space, like Technetium, that don't form naturally on Earth.
Could such non-terrestrial elements form also extraterrestrial minerals?
There are around 7,000 minerals known on Earth, but we still know little about other worlds in comparison. Over 300 minerals have been identified in meteorites. The number of minerals identified on planetary bodies is smaller and mainly detected by remote sensing or exploration with robots. Around 130 minerals were discovered so far on Mars and 80 on the Earth's Moon. As some of those minerals were formed under conditions that don't exist on Earth, such as low gravity, or the complete absence of liquid water, many are indeed unknown in the Earth's environments.
A curious scientific blooper. In the episode part of the landing party is stranded on the planet, as the transporter doesn't work, and it is mentioned that the temperatures on the surface drop to -120°C during nighttime. Such temperatures would be only possible on a planet without an atmosphere, where temperatures can drop to -200°C. On Earth the coldest temperature ever measured was -90°C during the Antarctic winter.
