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(repeating unit)
Strunz classification9.CJ.25
Dana classification61.01.04.02
Crystal systemMonoclinic
Crystal classPrismatic
H-M symbol: 2/m
Space groupB2/b
Unit cell3,179.12
Crystal habitTabular, common twinning
CleavagePerfect on {001}
Mohs scale hardness3.5 - 4
LusterVitreous, pearly
Optical propertiesBiaxial (+)
Ultraviolet fluorescencebrilliant blue-white under SW
Other characteristicsRadioactive.svg Radioactive

Katayamalite is a cyclosilicate mineral that was named in honor of mineralogist and professor Nobuo Katayama.[1]

Relation with baratovite[edit]

Katayamalite was approved in 1982 by the International Mineralogical Association. It is the hydroxyl analogue of baratovite and the hydroxyl end member of the series,[1] but was first described as a fluor-dominant mineral. Some scientists claim it to be rather hydroxyl- than fluor dominant, which would make baratovite isostructural with it. It would make the two minerals the same species, with baratovite having priority. As the case hadn't been clarified, katayamalite remains an IMA-approved mineral until this day.[2]

Chemical properties[edit]

Katayamalite mainly consists of oxygen (43.16%), silicon (24.25%), calcium (20.18%), but otherwise contains titanium (6.89%), potassium (2.81%), lithium (1.50%), fluorine (0.68%), sodium (0.41%) and hydrogen (0.11%). It has a barely detectable radioactivity, 40.21 measured in Gamma Ray American Petroleum Institute Units. The concentration of it in percentage is 2.49. It was originally described as having a triclinic symmetry in 1985, but the structure was redetermined to be monoclinic in 2013. It has a radiant blue-white fluorescence, and platy morphology. The mineral is associated with sugilite, albite and aegirine.[2] Crystals are usually twinned.[1]


  1. ^ a b c "Katayamalite Mineral Data". webmineral.com. Retrieved 2021-08-08.
  2. ^ a b "Katayamalite". www.mindat.org. Retrieved 2021-08-08.