Sputnik Aragonite is a popular collector's specimen characterized by its distinctive star-shaped or cross-shaped cyclic twinning patterns. These clusters form in sedimentary environments, most famously in the clay beds of Spain, often displaying a soft brown or tan hue with a sharp, geometric aesthetic.

Hardness

3.5-4

Mohs

Luster

Vitreous

Streak

White

Transparency

Translucent

mineralcommonAragonite family

Sputnik Aragonite

Hardness: 3.5-4
Luster: Vitreous
Streak: White
Transparency: Translucent

Is this sputnik aragonite?

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 sputnik aragonite with a known reference. Sputnik Aragonite sits at Mohs 3.5-4, 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: brown, tan, creamy white.
5
Look at form & habit
Crystal system: orthorhombic. Typical habit: star-shaped cyclic twin clusters.

Often confused with

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

mineral

Cerussite

Mohs 3-3.5

How to tell apart: Luster reads vitreous on Sputnik Aragonite and adamantine, tending toward vitreous, resinous on Cerussite.

Often found alongside sputnik aragonite

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

All properties

Chemical formula: CaCO₃
Mohs hardness: 3.5-4
Density: 2.95 g/cm³
Colors: Brown TanCreamy white
Streak: White
Luster: Vitreous
Transparency: Translucent
Crystal system: Orthorhombic
Crystal habit: Star-shaped cyclic twin clusters
Cleavage: Distinct on {010}
Fluorescence: Often bright yellow or cream under SW UV
Rarity: Common
Uses: Collector, Decorative
Host rock: sedimentary deposits in clay or gypsum beds

Where rockhounds find sputnik aragonite

Classic worldwide localities

Minglanilla, Spain
Taze, Morocco
Dzierżno, Poland

Field-hunting tip

Where it forms: sedimentary deposits in clay or gypsum beds. If you start seeing gypsum, calcite, sulfur in float, you are in the right ground. Typical habit: star-shaped cyclic twin clusters. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify sputnik aragonite?+

Mohs hardness is 3.5-4. Luster: vitreous. The streak is white. Common colors include brown, tan, creamy white.

Where is sputnik aragonite found?+

Notable localities include Minglanilla, Spain; Taze, Morocco; Dzierżno, Poland.

What rocks look like sputnik aragonite?+

Sputnik Aragonite is most often confused with Cerussite, Strontianite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with sputnik aragonite?+

Sputnik Aragonite commonly co-occurs with Gypsum, Calcite, Sulfur. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does sputnik aragonite form in?+

Where it forms: sedimentary deposits in clay or gypsum beds. Working float back to the host body is the standard way to chase a fresh occurrence.

What is sputnik aragonite used for?+

Sputnik Aragonite is used in collector, decorative.

Find sputnik aragonite on the map

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