RocksdayAbout Rocksday
Rocksday is a daily guessing game for anyone who picks up interesting stones. Each day there's one mystery rock, mineral or gem — guess it from a close-up photo in six tries, then learn how to recognize it in the field.
The rock library covers the specimens you're most likely to find, buy or be asked about, with practical identification tips and the lookalikes people most often mix up. The identifier narrows down an unknown specimen using simple tests you can do at home.
Sources
Properties are compiled from standard mineralogy references and cross-checked against public data such as Wikidata and the IMA list of minerals. Hardness values for rocks are practical approximations, since rocks are mixtures of minerals. Spotted a mistake? Email hello@rocksday.com.
Photo credits
All specimen photos come from Wikimedia Commons under free licenses. Thank you to the photographers.
- Agate — James St. John, CC BY 2.0
- Amber — Anders L. Damgaard - www.amber-inclusions.dk - Baltic-amber-beetle, CC BY-SA 4.0
- Amethyst — Gonzalo Devia, CC BY-SA 4.0
- Andesite — Photographer: Siim Sepp, 2005, CC BY-SA 3.0
- Apatite — Thomas Spann, CC BY 2.0
- Aragonite — JJ Harrison (https://www.jjharrison.com.au/), CC BY-SA 4.0
- Azurite — Ivar Leidus, CC BY-SA 4.0
- Barite — Ivar Leidus, CC BY-SA 4.0
- Basalt — James St. John, CC BY 2.0
- Beryl — Reno Chris at English Wikipedia, Public domain
- Biotite — Fred Kruijen, CC BY-SA 3.0 nl
- Breccia — No machine-readable author provided. Siim assumed (based on copyright claims)., CC BY-SA 3.0
- Calcite — Robert M. Lavinsky, CC BY-SA 3.0
- Celestine — Ivar Leidus, CC BY-SA 4.0
- Chalcopyrite — Robert M. Lavinsky, CC BY-SA 3.0
- Chalk — Nessa Eull, CC0
- Chert — Unknown, Public domain
- Cinnabar — H. Zell, CC BY-SA 3.0
- Coal — Amcyrus2012, CC BY 4.0
- Conglomerate — James St. John, CC BY 2.0
- Corundum — Ra'ike (see also Ra'ike on de.wikipedia, CC BY-SA 3.0
- Diamond — DGPC/ADF Luísa Oliveira, CC0
- Diorite — Michael C. Rygel, CC BY-SA 3.0
- Dolomite — Didier Descouens, CC BY-SA 4.0
- Epidote — Gleb Korovko, CC BY 4.0
- Fluorite — CarlesMillan, CC BY-SA 3.0
- Gabbro — Darla Sondrol, CC0
- Galena — Ivar Leidus, CC BY-SA 4.0
- Garnet — Moha112100, CC BY-SA 3.0
- Gneiss — No machine-readable author provided. Siim assumed (based on copyright claims)., CC BY-SA 3.0
- Gold — Alchemist-hp (talk) www.pse-mendelejew.de, CC BY-SA 3.0 de
- Granite — The stone gate, CC BY-SA 4.0
- Gypsum — Didier Descouens, CC BY-SA 4.0
- Halite — Lech Darski, CC BY-SA 4.0
- Hematite — Wikipedia Loves Art participant "Assignment_Houston_One", CC BY-SA 2.5
- Jasper — Tommy from Arad, CC BY 2.0
- Kyanite — User:Aelwyn, CC BY-SA 3.0
- Labradorite — Parent Géry, Public domain
- Lapis Lazuli — Hannes Grobe, CC BY-SA 2.5
- Limestone — Mike Davis, CC0
- Magnetite — Robert M. Lavinsky, CC BY-SA 3.0
- Malachite — JJ Harrison (https://www.jjharrison.com.au/), CC BY-SA 3.0
- Marble — Zyance, CC BY-SA 2.5
- Muscovite — Robert M. Lavinsky, CC BY-SA 3.0
- Native Copper — Native_Copper_Macro_Digon3.jpg: “Jonathan Zander (Digon3)" derivative work: Materialscientist (talk), CC BY-SA 3.0
- Obsidian — Ji-Elle It feels nice and warm It feels like a love storm, CC BY-SA 3.0
- Olivine — Robert M. Lavinsky, CC BY-SA 3.0
- Opal — Robert M. Lavinsky, CC BY-SA 3.0
- Orthoclase — Didier Descouens, CC BY-SA 4.0
- Pumice — User MPF on en.wikipedia, CC BY-SA 3.0
- Pyrite — Ivar Leidus, CC BY-SA 4.0
- Quartz — Didier Descouens, CC BY-SA 4.0
- Quartzite — Gabriel Haute Maurienne, CC BY-SA 4.0
- Rhodochrosite — JJ Harrison (https://www.jjharrison.com.au/), CC BY-SA 4.0
- Rhyolite — Benhoff, CC BY-SA 3.0
- Rose Quartz — James St. John, CC BY 2.0
- Sandstone — Unknown, Public domain
- Schist — Michael C. Rygel, CC BY-SA 3.0
- Scoria — ScoriaPumice, CC0
- Shale — James St. John, CC BY 2.0
- Slate — Dexter Perkins, CC0
- Soapstone — Ra'ike (see also: de:Benutzer:Ra'ike), CC BY-SA 3.0
- Sodalite — Ra'ike (see also: de:Benutzer:Ra'ike), CC BY-SA 3.0
- Sphalerite — Ivar Leidus, CC BY-SA 4.0
- Staurolite — Robert M. Lavinsky, CC BY-SA 3.0
- Sulfur — Ivar Leidus, CC BY-SA 4.0
- Talc — Unknown, Public domain
- Topaz — Parent Géry, CC BY-SA 3.0
- Tourmaline — Robert M. Lavinsky, CC BY-SA 3.0
- Turquoise — Robert M. Lavinsky, CC BY-SA 3.0