Wesselsite is a rare strontium copper silicate that occurs as vibrant deep purple platy crystals. It is primarily found within the manganese mines of the Kalahari Manganese Field in South Africa, often associated with other rare silicate minerals.

Hardness

4-5

Mohs

Streak

White to light blue

Transparency

Translucent

mineralrareGillespite Group family

Wesselsite

Hardness: 4-5
Streak: White to light blue
Transparency: Translucent

No image

Is this wesselsite?

4-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 wesselsite with a known reference. Wesselsite 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: white to light blue.
3
Match the color range
Compare against the expected color range: blue.
4
Look at form & habit
Crystal system: tetragonal. Typical habit: platy crystals.

Often confused with

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

mineral

Gillespite

Mohs 3-4

How to tell apart: Streak differs, so Wesselsite leaves white to light blue, Gillespite leaves pink.

How to tell apart: Streak differs, so Wesselsite leaves white to light blue, Cuprorivaite leaves light blue.

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Often found alongside wesselsite

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

All properties

Chemical formula: SrCuSi₄O₁₀
Mohs hardness: 4-5
Density: 3.2 g/cm³
Colors: Blue
Streak: White to light blue
Transparency: Translucent
Crystal system: Tetragonal
Crystal habit: Platy crystals
Cleavage: Perfect on {001}
Rarity: Rare
Uses: Collector, Scientific research
Host rock: In a hydrothermally-altered sedimentary manganese deposit

Where rockhounds find wesselsite

Classic worldwide localities

Wessels mine, Kalahari Manganese field, Kuruman Hill, Cape Province, South Africa (type locality)

Field-hunting tip

Where it forms: In a hydrothermally-altered sedimentary manganese deposit. If you start seeing hennomartinite, sugulite, pectolite in float, you are in the right ground. Typical habit: platy crystals. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify wesselsite?+

Mohs hardness is 4-5. The streak is white to light blue. Common colors include blue.

Where is wesselsite found?+

Notable localities include Wessels mine, Kalahari Manganese field, Kuruman Hill, Cape Province, South Africa (type locality).

Is wesselsite safe to handle?+

Wesselsite contains copper. Wash your hands afterwards, never grind or breathe the dust, and store it apart from specimens you handle often.

What rocks look like wesselsite?+

Wesselsite is most often confused with Gillespite, Cuprorivaite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with wesselsite?+

Wesselsite commonly co-occurs with Hennomartinite, Sugulite, Pectolite, Xonotlite, Quartz. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does wesselsite form in?+

Where it forms: In a hydrothermally-altered sedimentary manganese deposit. Working float back to the host body is the standard way to chase a fresh occurrence.

What is wesselsite used for?+

Wesselsite is used in collector, scientific research.

Find wesselsite on the map

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