Seidite-(Ce) is an extremely rare silicate mineral characterized by its thin, fragile tabular crystal habit and yellow-to-brown coloration. It is primarily found as an accessory mineral in complex agpaitic alkaline pegmatites, most notably within the Khibiny Massif in Russia. Collectors prize it for its unique chemical structure, though its rarity makes high-quality display specimens difficult to acquire.
Is this seidite-(ce)?
4-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry to scratch seidite-(ce) with a known reference. Seidite-(Ce) sits at Mohs 3-4, softer than the next harder reference, harder than the previous one.
- 2Read the lusterHold the specimen under a strong light. Luster: vitreous to silky, resinous or dull in some specimens.
- 3Match the color rangeCompare against the expected color range: yellow, pinkish yellow, cream.
- 4Look at form & habitCrystal system: monoclinic. Typical habit: aggregates, fibrous, radial.
Often confused with
Seidite-(Ce) vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Labuntsovite is the harder of the two (Mohs 6 vs. 3-4); luster reads vitreous to silky, resinous or dull in some specimens on Seidite-(Ce) and greasy on Labuntsovite.
How to tell apart: Nenadkevichite is the harder of the two (Mohs 5 vs. 3-4).
Often found alongside seidite-(ce)
Minerals reported to co-occur with seidite-(ce). Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Na₄(Ce,Sr)₂TiSi₈O₁₈(O,OH,F)₆(H₂O)₅
- Mohs hardness
- 3-4
- Density
- 2.76 g/cm³
- Luster
- Vitreous to silky, resinous or dull in some specimens
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Aggregates, fibrous, radial
- Cleavage
- Perfect {100}; less perfect {001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Sparingly in cavernous natrolite in an ultra-agpaitic pegmatite vein
Where rockhounds find seidite-(ce)
Classic worldwide localities
- Yubileynaya pegmatite vein, Mount Karnasurt, Lovozero alkaline massif, Kola Peninsula, Russia
Field-hunting tip
Where it forms: Sparingly in cavernous natrolite in an ultra-agpaitic pegmatite vein. If you start seeing belovite, vitusite, sazhinite- in float, you are in the right ground. Typical habit: aggregates, fibrous, radial. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify seidite-(ce)?+
Where is seidite-(ce) found?+
What rocks look like seidite-(ce)?+
What minerals are found with seidite-(ce)?+
What kind of rock does seidite-(ce) form in?+
What is seidite-(ce) used for?+
Find seidite-(ce) on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
