Pseudomarkeyite is a rare pseudomorph where calcium carbonate (calcite) has replaced the unstable mineral ikaite, which typically forms in cold marine sediments. Collectors prize these for their unique, often elongated or 'fleur-de-lis' crystal shapes that retain the structural history of the original ikaite phase. They are typically found in glacial-marine sediments and require careful handling due to the fragile nature of these pseudomorphs.

Hardness

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrareCalcite family

Pseudomarkeyite

Hardness: 3
Luster: Vitreous
Streak: White
Transparency: Transparent

No image

Is this pseudomarkeyite?

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 pseudomarkeyite with a known reference. Pseudomarkeyite sits at Mohs 3, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Pseudomarkeyite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Pseudomarkeyite typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: white, colorless, gray.
5
Look at form & habit
Crystal system: trigonal. Typical habit: pseudomorphs after ikaite.

Often confused with

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

Often found alongside pseudomarkeyite

Minerals reported to co-occur with pseudomarkeyite. 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
Density: 2.71 g/cm³
Colors: White Colorless Gray
Streak: White
Luster: Vitreous
Transparency: Transparent
Crystal system: Trigonal
Crystal habit: Pseudomorphs After Ikaite
Cleavage: Perfect Rhombohedral
Rarity: Rare
Uses: Collector
Host rock: Sedimentary Marine Deposits
Typical price: $20-150 per specimen

Where rockhounds find pseudomarkeyite

Classic worldwide localities

Greenland
Canada
Norway

Field-hunting tip

Look in sedimentary marine deposits country, the host setting where pseudomarkeyite typically forms. If you start seeing calcite, aragonite in float, you are in the right ground. Field specimens usually show a pseudomorphs after ikaite habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify pseudomarkeyite?+

Mohs hardness is 3. It typically shows a vitreous luster. The streak is white. Common colors include white, colorless, gray.

Where is pseudomarkeyite found?+

Notable localities include Greenland; Canada; Norway.

How much is pseudomarkeyite worth?+

Typical asking prices fall in the range of $20-150 per specimen. Quality, size, and provenance can move individual specimens well outside that range.

What rocks look like pseudomarkeyite?+

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

What minerals are found with pseudomarkeyite?+

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

What kind of rock does pseudomarkeyite form in?+

Pseudomarkeyite typically forms in sedimentary marine deposits. Working float back to the host body is the standard way to chase a fresh occurrence.

What is pseudomarkeyite used for?+

Pseudomarkeyite is used in collector.

Find pseudomarkeyite on the map

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