Huizingite-(Al) is an extremely rare ammonium-aluminum sulfate mineral first identified in the Hagendorf-Sud pegmatite of Bavaria. It typically occurs as tiny, distinct yellow tabular crystals within cavities in phosphate-rich pegmatite environments. Collectors usually encounter this only as micro-mount specimens due to the rarity of its discovery sites.

Hardness

2.5

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrare

Huizingite-(Al)

Hardness: 2.5
Luster: Vitreous
Streak: White
Transparency: Transparent

No image

Is this huizingite-(al)?

5-step field check

Run through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.

1
Test the hardness
Try to scratch huizingite-(al) with a known reference. Huizingite-(Al) sits at Mohs 2.5, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Streak: white.
3
Read the luster
Hold the specimen under a strong light. Luster: vitreous.
4
Match the color range
Compare against the expected color range: yellow, yellowish-orange.
5
Look at form & habit
Crystal system: triclinic. Typical habit: tabular crystals.

Often confused with

Huizingite-(Al) vs. its common look-alikes, and how to tell them apart in the field.

mineral

Tschermigite

Mohs 1.5

How to tell apart: Huizingite-(Al) is noticeably harder (Mohs 2.5 vs. 1.5).

How to tell apart: Alunite is the harder of the two (Mohs 3.5-4 vs. 2.5).

Compare →

Often found alongside huizingite-(al)

Minerals reported to co-occur with huizingite-(al). Spotting these in float or country rock is a strong cue you are in the right ground.

All properties

Chemical formula: (NH₄)₃Al(SO₄)₂(OH)₂·H₂O
Mohs hardness: 2.5
Density: 2.026 g/cm³
Colors: Yellow Yellowish-orange
Streak: White
Luster: Vitreous
Transparency: Transparent
Crystal system: Triclinic
Crystal habit: Tabular crystals
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: Formed by a natural fire in oil-bearing shale exposed along a cliff

Where rockhounds find huizingite-(al)

Classic worldwide localities

Huron River burn site, ~6 km west southwest of Milan, Ohio, USA

Field-hunting tip

Where it forms: Formed by a natural fire in oil-bearing shale exposed along a cliff. If you start seeing adranosite-, anhydrite, boussingaultite in float, you are in the right ground. Typical habit: tabular crystals. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify huizingite-(al)?+

Mohs hardness is 2.5. Luster: vitreous. The streak is white. Common colors include yellow, yellowish-orange.

Where is huizingite-(al) found?+

Notable localities include Huron River burn site, ~6 km west southwest of Milan, Ohio, USA.

What rocks look like huizingite-(al)?+

Huizingite-(Al) is most often confused with Tschermigite, Alunite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with huizingite-(al)?+

Huizingite-(Al) commonly co-occurs with Adranosite-, Anhydrite, Boussingaultite, Mascagnite, Salammoniac. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does huizingite-(al) form in?+

Where it forms: Formed by a natural fire in oil-bearing shale exposed along a cliff. Working float back to the host body is the standard way to chase a fresh occurrence.

What is huizingite-(al) used for?+

Huizingite-(Al) is used in collector.

Find huizingite-(al) on the map

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