Gemdle

Gemdle is a mineral-identification game based on photos of real specimens: one image, four names, and the question "Which crystal is this?" The daily challenge strings together five stones, numbered and tracked as a series; alongside it, a free-play mode lets you run endless rounds. But the game is only the gateway to a documentary site, with an identification tool that filters by color, luster, hardness and transparency to propose a ranked list of candidates, a guide of more than 250 stones and color-based navigation. The editorial line is explicit on the homepage: the site sets aside the esoteric side of the subject to stick to what can be observed and tested, and it cites its sources, with photos and physical properties coming from Wikimedia Commons and Wikipedia, plus the photographer credit and licence under each image.

1. Choose between the daily five-stone challenge and free play, both accessible from the top bar.
2. Study the specimen photo, presented as-is, with the photographer credit beneath it.
3. Click one of the four offered names.
4. Continue: the daily challenge shows progress out of five; free play restarts indefinitely.
5. Switch to the identification tool or the stone’s page to learn what distinguishes it from look-alikes.

Many daily games stop at the riddle; Gemdle has the good idea of connecting its riddle to a complete documentary apparatus. You play out of curiosity and stay because the site extends the quiz with a guide of more than 250 stones and their physical properties, and because the identification tool gives the game concrete utility the day you pick up an intriguing rock. The choice of sources, photos and data credited to Wikimedia Commons and Wikipedia, and the explicit rejection of the esoteric register give the whole thing an honesty rare in a field saturated with sales pitches. The primary pleasure remains: four similar names, a photo of a rough specimen, and the discovery that color, the first reflex for everyone, is often the worst clue.

The quiz is multiple choice among four names, with a streak counter marked by a flame at the top of the round and a numeric progression for the daily challenge. The homepage also promises to show why an answer was right or wrong and to allow sharing your score.

Daily

The daily challenge: five stones in a row, numbered and tied to the streak counter.

Free play

Free play, described as endless practice: you run through photos for as long as you want. Its page invites you to return to the daily five-stone challenge to build your streak.

• Free play also displays a streak counter, and its page invites you to return to the daily five-stone challenge to build it.
• The site itself reminds you that the same mineral often appears in several colors: hue alone doesn't decide.
• The real differentiators are those the site highlights in its guide (luster, Mohs hardness, streak and habit), so look at surface appearance and growth form in the photo rather than the dominant color.
• The identification tool is not an advertising gimmick: it filters on criteria you can actually observe at home and returns a ranked list, with a footer warning that it is neither gemological expertise nor buying advice.