Siudaite is an extremely rare member of the eudialyte group typically found in agpaitic pegmatites on the Kola Peninsula. It most commonly occurs as small, tabular, yellow-tinted crystals in association with other rare alkaline minerals. Identification usually requires professional analysis due to its striking similarity to other eudialyte-group members.

Hardness

4.5

Mohs

Luster

Vitreous

Streak

White

Transparency

Translucent

mineralrareEudialyte Group family

Siudaite

Hardness: 4.5
Luster: Vitreous
Streak: White
Transparency: Translucent

Is this siudaite?

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 siudaite with a known reference. Siudaite 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.
3
Read the luster
Hold the specimen under a strong light. Luster: vitreous.
4
Match the color range
Compare against the expected color range: yellow, brownish yellow.
5
Look at form & habit
Crystal system: trigonal. Typical habit: tabular crystals.

Often confused with

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

Often found alongside siudaite

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

All properties

Chemical formula: Na₈(Mn₂Na)Ca₆Fe₃Zr₃NbSi₂₅O₇₄(OH)₂Cl(H₂O)₅
Mohs hardness: 4.5
Density: 2.96 g/cm³
Colors: Yellow Brownish yellow
Streak: White
Luster: Vitreous
Transparency: Translucent
Crystal system: Trigonal
Crystal habit: Tabular crystals
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: A product of the hydrothermal alteration of a primary eudialyte-group mineral presumably related to georgbarsanovite, in a peralkaline pegmatite

Where rockhounds find siudaite

Classic worldwide localities

Astrophyllitovyi Stream valley, Mt. Eveslogchorr, Khibiny alkaline massif, Kola Peninsula, Russia

Field-hunting tip

Where it forms: A product of the hydrothermal alteration of a primary eudialyte-group mineral presumably related to georgbarsanovite, in a peralkaline pegmatite. If you start seeing aegirine, albite, microcline 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 siudaite?+

Mohs hardness is 4.5. Luster: vitreous. The streak is white. Common colors include yellow, brownish yellow.

Where is siudaite found?+

Notable localities include Astrophyllitovyi Stream valley, Mt. Eveslogchorr, Khibiny alkaline massif, Kola Peninsula, Russia.

What rocks look like siudaite?+

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

What minerals are found with siudaite?+

Siudaite commonly co-occurs with Aegirine, Albite, Microcline, Nepheline, Astrophyllite, Loparite-. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does siudaite form in?+

Where it forms: A product of the hydrothermal alteration of a primary eudialyte-group mineral presumably related to georgbarsanovite, in a peralkaline pegmatite. Working float back to the host body is the standard way to chase a fresh occurrence.

What is siudaite used for?+

Siudaite is used in collector.

Find siudaite on the map

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