Diadochite is an uncommon hydrated iron phosphate-sulfate mineral that typically forms as botryoidal or reniform crusts in the oxidized zones of ore deposits. It is often confused with the related species delvauxite, as both frequently exhibit similar waxy, resinous textures and earthy colors. Collectors should look for these distinct, often rounded masses in environments where pyrite and other sulfide minerals have undergone significant weathering.
Is this diadochite?
5-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry to scratch diadochite with a known reference. Diadochite sits at Mohs 3-4, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: yellow.
- 3Read the lusterHold the specimen under a strong light. Luster: waxy.
- 4Match the color rangeCompare against the expected color range: yellow, brown, yellowish green, cinnamon brown, yellowish white.
- 5Look at form & habitCrystal system: amorphous. Typical habit: encrustations, nodular, stalactitic.
Often confused with
Diadochite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Diadochite leaves yellow, Delvauxite leaves pale brown.
How to tell apart: Gorceixite is the harder of the two (Mohs 6 vs. 3-4); streak differs, so Diadochite leaves yellow, Gorceixite leaves white; luster reads waxy on Diadochite and vitreous on Gorceixite.
Often found alongside diadochite
Minerals reported to co-occur with diadochite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Fe³⁺₂(PO₄)(SO₄)(OH)·6H₂O
- Mohs hardness
- 3-4
- Density
- 2.0-2.4 g/cm³
- Colors
- Streak
- Yellow
- Luster
- Waxy
- Transparency
- Semitransparent
- Crystal system
- Amorphous
- Crystal habit
- Encrustations, nodular, stalactitic
- Cleavage
- None
- Rarity
- Uncommon
- Uses
- Collector, Scientific research
- Host rock
- A secondary mineral in gossans and some coal deposits, formed by sulfate-rich solutions acting on earlier phosphates, may be post-mine; in cave deposits, the phosphate derived from guano
Where rockhounds find diadochite
Classic worldwide localities
- Bethel Church, Pike Co., Indiana, USA
- A coal mine in Jackson Township, Coshocton Co., and in Monday Creek Township, Perry Co., Ohio, USA
- Coon Creek mine, near Shady, Polk Co., Arkansas, USA
- Tip Top mine, 8.5 km southwest of Custer, Custer Co., South Dakota, USA
- Arnsbach (type locality), near Gräfenthal, and in the Garnsdorf mine and the Feengrotten (Cave), Saalfeld, Thuringia, Germany
- Visé, Védrin, and Haut-le-Wastia, Belgium
Field-hunting tip
Where it forms: A secondary mineral in gossans and some coal deposits, formed by sulfate-rich solutions acting on earlier phosphates, may be post-mine; in cave deposits, the phosphate derived from guano. If you start seeing delvauxite, vashegyite, pitticite in float, you are in the right ground. Typical habit: encrustations, nodular, stalactitic. Train your eye for that shape before scanning the outcrop.
Common questions
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What rocks look like diadochite?+
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Find diadochite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
