Cerchiaraite-(Al) is a rare silicate mineral primarily found in the manganese-rich deposits of the Cerchiara mine in Italy. It typically occurs as small, blue to greenish blue tabular crystals, often forming in association with manganese minerals like braunite within metasedimentary host rocks.

Hardness

~4.5

Mohs

Luster

Vitreous

Streak

Pale green-blue

Transparency

Transparent

mineralrare

Cerchiaraite-(Al)

Hardness: ~4.5
Luster: Vitreous
Streak: Pale green-blue
Transparency: Transparent

Is this cerchiaraite-(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 cerchiaraite-(al) with a known reference. Cerchiaraite-(Al) sits at Mohs ~4.5, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Streak: pale green-blue.
3
Read the luster
Hold the specimen under a strong light. Luster: vitreous.
4
Match the color range
Compare against the expected color range: blue, greenish blue, bluish green.
5
Look at form & habit
Crystal system: tetragonal. Typical habit: tabular crystals, subhedral grains.

Often confused with

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

mineral

Cerchiaraite-(Fe)

Mohs ~4.5

How to tell apart: Streak differs, so Cerchiaraite-(Al) leaves pale green-blue, Cerchiaraite-(Fe) leaves colorless to tan or pale green-blue.

Compare →

Often found alongside cerchiaraite-(al)

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

All properties

Chemical formula: Ba₄Al₄(Si₄O₁₂)O₂(OH)₄Cl₂[Si₂O₃(OH)₄]
Mohs hardness: ~4.5
Density: 3.69 g/cm³
Colors: Blue Greenish blue Bluish green
Streak: Pale green-blue
Luster: Vitreous
Transparency: Transparent
Crystal system: Tetragonal
Crystal habit: Tabular crystals, subhedral grains
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: Formed on the margins of quartz-sanbornite veins as a result of fluid interactions

Where rockhounds find cerchiaraite-(al)

Classic worldwide localities

Esquire No. 1, Rush Creek, and Esquire No. 7 and No. 8 claims, Big Creek, Fresno County, California, USA

Field-hunting tip

Where it forms: Formed on the margins of quartz-sanbornite veins as a result of fluid interactions. If you start seeing bazirite, diopside, goethite in float, you are in the right ground. Typical habit: tabular crystals, subhedral grains. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify cerchiaraite-(al)?+

Mohs hardness is ~4.5. Luster: vitreous. The streak is pale green-blue. Common colors include blue, greenish blue, bluish green.

Where is cerchiaraite-(al) found?+

Notable localities include Esquire No. 1, Rush Creek, and Esquire No. 7 and No. 8 claims, Big Creek, Fresno County, California, USA.

What rocks look like cerchiaraite-(al)?+

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

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

Cerchiaraite-(Al) commonly co-occurs with Bazirite, Diopside, Goethite, Opal, Quartz, Sanbornite. Spotting any of these in float or country rock is a useful trip signal.

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

Where it forms: Formed on the margins of quartz-sanbornite veins as a result of fluid interactions. Working float back to the host body is the standard way to chase a fresh occurrence.

What is cerchiaraite-(al) used for?+

Cerchiaraite-(Al) is used in collector.

Find cerchiaraite-(al) on the map

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