Zigrasite is an exceptionally rare magnesium-zirconium phosphate mineral found in highly evolved granite pegmatites. It typically occurs as small, clear tabular crystals and is highly prized by advanced micromount collectors due to its limited global occurrences.

Hardness

Mohs

Luster

Vitreous

Streak

White

Transparency

Translucent

mineralrare

Zigrasite

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

Is this zigrasite?

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 zigrasite with a known reference. Zigrasite 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. 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: off-white, pale-yellow.
5
Look at form & habit
Crystal system: triclinic. Typical habit: tabular crystals.

Often confused with

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

mineral

Morinite

Mohs 4-4.5

How to tell apart: Morinite is the harder of the two (Mohs 4-4.5 vs. 3).

How to tell apart: Roscherite is the harder of the two (Mohs 4.5 vs. 3); streak differs, so Zigrasite leaves white, Roscherite leaves light brown.

Compare →

Often found alongside zigrasite

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

All properties

Chemical formula: MgZr(PO₄)₂·4H₂O
Mohs hardness: 3
Density: 2.76 g/cm³
Colors: Off-whitePale-yellow
Streak: White
Luster: Vitreous
Transparency: Translucent
Crystal system: Triclinic
Crystal habit: Tabular crystals
Cleavage: Imperfect on (010) and (001)
Rarity: Rare
Uses: Collector
Host rock: One of the last minerals formed in a tourmaline-bearing pocket in a complex rare-element granitic pegmatite

Where rockhounds find zigrasite

Classic worldwide localities

Tip Top mine, South Dakota, USA

Field-hunting tip

Where it forms: One of the last minerals formed in a tourmaline-bearing pocket in a complex rare-element granitic pegmatite. If you start seeing tourmaline, microcline, quartz in float, you are in the right ground. Typical habit: tabular crystals. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify zigrasite?+

Mohs hardness is 3. Luster: vitreous. The streak is white. Common colors include off-white, pale-yellow.

Where is zigrasite found?+

Notable localities include Tip Top mine, South Dakota, USA.

What rocks look like zigrasite?+

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

What minerals are found with zigrasite?+

Zigrasite commonly co-occurs with Tourmaline, Microcline, Quartz, Albite, Beryl, Amblygonite-montebrasite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does zigrasite form in?+

Where it forms: One of the last minerals formed in a tourmaline-bearing pocket in a complex rare-element granitic pegmatite. Working float back to the host body is the standard way to chase a fresh occurrence.

What is zigrasite used for?+

Zigrasite is used in collector.

Find zigrasite on the map

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