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Identity HelpIdentity help. Pink mineral in granite

24th May 2020 14:50 UTCJyrki Autio Expert

08529530016027239402784.jpg
What might be this mineral from pegmatite vein in microcline granite?
Kovela, Finland
Hardness 3. Conchoidal fracture.
Exists as irregular grains to 1 cm in microcline.
Directly in contact with biotite, microcline and monazite.
Seems to shrink and crack on weathered surface rock. Does not dissolve with time.

In picture small yellow crystals are monazite. FOV 4mm

Thank you

24th May 2020 14:51 UTCJyrki Autio Expert

03990740016027239411111.jpg
Another picture with monazite. FOV 3 mm

24th May 2020 15:15 UTCAlfredo Petrov Manager

Sounds like a clay mineral.

24th May 2020 16:13 UTCJyrki Autio Expert

Possibly halloysite in this environment?  Halloysite also seems to be on the harder side of clay minerals.

25th May 2020 02:05 UTCHarold Moritz 🌟 Expert

Does it fluoresce?

25th May 2020 12:24 UTCJyrki Autio Expert

No fluorescence.
I tested hardness again and it is between 2 and 3.

25th May 2020 13:43 UTCA. M.

Agree with Alfredo - it looks like clay mineral. Smectite group - montmorillonite, saponite...?

25th May 2020 13:47 UTCLuís Martins 🌟

opal?

25th May 2020 17:14 UTCJyrki Autio Expert

Thanks for replies,

This is too soft for opal.
Clay mineral replacing plagioclase perhaps.


25th May 2020 18:46 UTCAlfredo Petrov Manager

Check for lithium. Might be some Li-rich clay found in pegmatites, like swinefordite? 
And your first assumption of halloysite could be possible too.
 
Mineral and/or Locality  
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