Giacovazzoite is a rare hydrated iron potassium sulfate mineral identified primarily from fumarolic environments. Collectors typically find it as small, orange tabular crystals associated with other sulfate minerals in volcanic settings.
Is this giacovazzoite?
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 giacovazzoite with a known reference. Giacovazzoite sits at Mohs 2 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Giacovazzoite leaves a yellowish-orange streak.
- 3Read the lusterHold the specimen under a strong light. Giacovazzoite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: orange, reddish-orange.
- 5Look at form & habitCrystal system: triclinic. Typical habit: tabular crystals.
Often confused with
Giacovazzoite vs. its common look-alikes — and how to tell them apart in the field.

How to tell apart: Streak differs — Giacovazzoite leaves yellowish-orange, Jarosite leaves yellow.

How to tell apart: Streak differs — Giacovazzoite leaves yellowish-orange, Copiapite leaves yellow; luster reads vitreous on Giacovazzoite and pearly on Copiapite.
Often found alongside giacovazzoite
Minerals reported to co-occur with giacovazzoite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- K₅Fe³⁺₃O(SO₄)₆·9H₂O
- Mohs hardness
- 2
- Density
- 2.44 g/cm³
- Colors
- Streak
- Yellowish-orange
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Triclinic
- Crystal habit
- Tabular Crystals
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Fumarolic Deposits
- Typical price
- $50-300 per specimen
Where rockhounds find giacovazzoite
Classic worldwide localities
- Tuscany, Italy
Field-hunting tip
Look in fumarolic deposits country — that is the host setting where giacovazzoite typically forms. If you start seeing jarosite, gypsum in float, you are in the right ground. Field specimens usually show a tabular crystals habit, so train your eye for that shape before scanning the outcrop.

