Sigloite is a rare phosphate mineral typically found as a secondary oxidation product in tin-bearing hydrothermal deposits. It is most frequently encountered as small, tabular, yellowish crystals often associated with other phosphate minerals like vauxite and paravauxite.

Hardness

3.5

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrareParavauxite Group family

Sigloite

Hardness: 3.5
Luster: Vitreous
Streak: White
Transparency: Transparent

Is this sigloite?

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 sigloite with a known reference. Sigloite sits at Mohs 3.5, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Sigloite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Sigloite typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: yellow, brownish-yellow, colorless.
5
Look at form & habit
Crystal system: orthorhombic. Typical habit: tabular crystals, radiating clusters.

Often confused with

Sigloite vs. its common look-alikes, and how to tell them apart in the field.

Often found alongside sigloite

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

All properties

Chemical formula: Fe³⁺Al₂(PO₄)₂(OH)₂·8H₂O
Mohs hardness: 3.5
Density: 2.7 g/cm³
Colors: Yellow Brownish-yellow Colorless
Streak: White
Luster: Vitreous
Transparency: Transparent
Crystal system: Orthorhombic
Crystal habit: Tabular Crystals, Radiating Clusters
Cleavage: Distinct
Rarity: Rare
Uses: Collector
Host rock: Hydrothermal Tin Deposits
Typical price: $50-300 per thumbnail specimen

Where rockhounds find sigloite

Classic worldwide localities

Llallagua, Bolivia
Hagendorf, Germany
Sapucaia pegmatite, Brazil

Field-hunting tip

Look in hydrothermal tin deposits country, the host setting where sigloite typically forms. If you start seeing vauxite, paravauxite, metavauxite in float, you are in the right ground. Field specimens usually show a tabular crystals, radiating clusters habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify sigloite?+

Mohs hardness is 3.5. It typically shows a vitreous luster. The streak is white. Common colors include yellow, brownish-yellow, colorless.

Where is sigloite found?+

Notable localities include Llallagua, Bolivia; Hagendorf, Germany; Sapucaia pegmatite, Brazil.

How much is sigloite worth?+

Typical asking prices fall in the range of $50-300 per thumbnail specimen. Quality, size, and provenance can move individual specimens well outside that range.

What rocks look like sigloite?+

Sigloite is most often confused with Vauxite, Paravauxite, Metavauxite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with sigloite?+

Sigloite commonly co-occurs with Vauxite, Paravauxite, Metavauxite, Vivianite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does sigloite form in?+

Sigloite typically forms in hydrothermal tin deposits. Working float back to the host body is the standard way to chase a fresh occurrence.

What is sigloite used for?+

Sigloite is used in collector.

Find sigloite on the map

RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.