Rock Theme Naming

No, this trope isn't about people named after rock stars. Some fiction named characters after things that can be dug from the ground, such as rocks, gems, metals, and minerals.

Naming women after jewels is the least conspicuous - it is quite common to gives girls names like Ruby, Opal, or Crystal, and Beryl used to be a common girl's name. Using the other variants tends to attract attention.

Anime and Manga

 * Beast King GoLion (The original source of Lion Voltron) has the original five pilots with surnames which are types of metal: Akira ("Keith") Kogane -- "gold", Isamu "Lance" Kurogane -- "iron", and so on. (Princess Fala/"Allura" doesn't fit into the scheme.)
 * CLAMP's four-volume series Wish uses this for the majority of named characters. The theme is precious and semi-precious stones. Names include: Kohaku ("Amber"), Hisui ("Jade"), Ruri ("Blue Glass"/"Lapis-lazuli"), Hari ("Crystal"), Koryuu ("Garnet"), Kokuyo ("Obsidian"), Sango ("Coral"), and Shinju ("Pearl"). There may be more.
 * In Inuyasha, the three characters from the youkai exterminator village who are actually named all have names related to semiprecious stones: Sango (coral), Kohaku (amber), and Kirara (mica).
 * Magnes is Latin for "lodestone", or magnetic iron. One example of an entity named for such is the Wizard in Mega Man Star Force 3 - the one piloting the rocket that almost blew up at Echo Ridge Elementary.
 * Sailor Moon's villains are frequently named after minerals or jewels, with varying obscurity. This began with the first-season villains, who are in fact named exclusively for green-colored jewels and minerals.
 * Only in English. Malachite's Japanese name is Kunzite, which is a pinkish stone that bleaches clear in the sun (perhaps that's why his hair is white?)
 * In Shaman King, several of the Native American shamans are named after metals: Silva (silver), Goldva, Kalim (from kalium, the German word for potassium), Nichrome (who has a brother named Chrome), Bron (bronze), Rutherfor (rutherfordium), and Zinc.
 * In Tsukihime, the Meido twins are named Hisui (Jade) and Kohaku (Amber).
 * The Manhwa Les Bijoux used this in spades. The main character had a Literal Split Personality - he was Lapis, she was Lazuli, and both of them hated prince Sapphire (well, Lazuli a tiny bit less, to his/her confusion and anger).
 * In Cardcaptor Sakura, Eriol's guardians/servants, Spinel Sun and Ruby Moon, are both named after gemstones often mistaken for each other.

Comic Books

 * Marvel Comics's Crystar Crystal Warrior was made of this trope. Names include Crystar, Moltar, Feldspar, Ambara, Stalax, Ogeode, Malachon (for Malachite), and their whole planet is named Crystallium.
 * DC Comics has Amethyst, Princess of Gemworld - in addition to the titular Amethyst, characters included Dark Opal, Carnelian, Emerald, Topaz, and Turquoise.

Fan Works

 * In Shining Pretty Cure, not just with the main heroines and the mascots, but the locations, which show a heavy light and gemstone motif. The story is set in Luminous Town, they attend Bright Academy, and congregate at Gemstone Park by Lake Lapis...

Film

 * Used in Akira Kurosawa's film August Rhapsody (the one about Nagasaki, with a guest appearance by Richard Gere as a half-Japanese pinapple company heir), when the Grandmother is listing all the metal-themed names of her siblings (Gin/silver, Kin/gold, Tetsuo/iron, etc... there were a lot of them) to jog her memory and see if Gere's character's recently deceased father could be among them, to the greedy hope of the Grandmother's grown children.
 * In the Hellboy films, the redshirts at the BPRD all have mineral-themed names such as Steel and Flint.

Literature

 * In Gene Wolfe's Book of the Long Sun, robots are named after gems, metal, or rocks, while humans males are named after animals or animal products (e.g. the main character Silk) and human females are named after plants (e.g. the love interest Hyacinth).
 * In the Discworld books, all trolls are named in some way after rocks or minerals. Female trolls tend to have the names of precious stones, whereas males tend to be named after more mundane minerals or rock formations such as "Cliff". (One book, however, features a troll called Big Jim Beef. This is explained as a "macho" nickname, similar to a human being called Rocky.)
 * In J. R. R. Tolkien's Middle-earth (The Lord of the Rings, etc), the hobbits do have an acknowledged tradition of most often naming females after flowers or gemstones, such as Diamond Took, Esmeralda Brandybuck or Ruby Gamgee.
 * In Double Act by Jaqueline Wilson, the protagonists are twins called Garnet and Ruby. Their mother was called Opal.
 * In Flavia Bujor's The Prophecy of the Stones the heroines are called Jade, Amber and Opal.
 * In the Bardic Voices series by Mercedes Lackey, Rune has a job as a musician at a brothel where all the ladies working there take on names after gems. The Madam goes by Amber, and the other ladies are called Sapphire, Pearl, Topaz, Ruby, Diamond, and Amethyst

Video Games

 * Tales of Hearts has its main characters named after minerals: Shing (last name Meteoryte), Kohak, Hisui, Innes Lorenz(inite), Beryl Benito, and Kunzite. For those of you who missed it, Kohak and Hisui are sister and brother, and their names are Amber and Jade respectively in Japanese. Supporting characters are named Chalcedny, Peridot, Byrocks, Paraiba... and the old party contains names like Iola, Tekta, and Labrado(rite)... and the Big Bad is ... I'll just stop now.
 * Early-game villains are named Grossular and Kornerupine, while the Big Bad's posse consists of Corundum, Clinoseraph, Chlorseraph, Geo Strigau, and Incarose. Look them all up.
 * The Jumi in Legend of Mana are all named after the gemstones in their cores. So when you run into a Jewel Thief named, a Gem Merchant named  , and hear of a Jumi Knight called  , it's not hard to put two and two together.
 * The Pokémon series has second-generation games Gold, Silver, and Crystal; third-generation games Ruby, Sapphire, and Emerald; and the fourth-generation games Diamond, Pearl, and Platinum. These names carried over to some characters in the manga.
 * Also, there was Pewter City with Brock who used Onix and Geodude.
 * Many rock/ground Pokemon named this way. Examples include Geodude, Graveller, Sandslash, Sandshrew, Regirock, Lunastone, Solrock.
 * Steelix and Registeel could be this as well.
 * As for Japanese names, from the fifth generation, there's Ishizumai and Iwaparesu. "Ishi" is "stone" and "Iwa" is "rock"
 * In the KOEI crossover game Warriors Orochi, the large boar-like generals (with the exception of Gyūki) are all named after minerals such as Feldspar and Galena.

Western Animation

 * The Flintstones (as well as the Rubbles, Mr. Slate, Joe Rockhead, etc.). Hey, they are a modern stone-age family.
 * The Guatemala Clan in Gargoyles are named Zafiro, Turquesa, Obsidiana, and Jade. They're Spanish, but you can probably figure out what they mean.
 * The main girls in Trollz are named for jewels: Amethyst, Ruby, Topaz, Sapphire, and Onyx. There are also other characters named for regular stones: Shale, Mica, Coal, Rock, and Jasper are just a few examples.

Real Life - Sports

 * When they're not using Animal Theme Naming, Australia's national sports teams (especially women's teams) tend to do this:
 * Opals (Women's basketball)
 * Sapphires (Women's under-21 basketball)
 * Gems (Women's under-19 basketball)
 * Pearls (Women's intellectual disability basketball)
 * Diamonds (Netball)