Shimazakiite

Ca2B2O5
IMA status
  • Approved
IMA symbol
Smz
IMA approved
2010
Also known as
  • IMA2010-085a
  • Shimazakiiet

Where it forms, where it's found

Geological setting

In irregular vein in crystalline limestone near gehlenite-spurrite skarns

Type locality
Fuka mine
  1. Fuka
  2. Bitchū
  3. Takahashi City
  4. Okayama Prefecture
  5. Japan

34.7882°, 133.4429°

1recorded occurrences
Source · OpenStreetMap

Physical

Colour
Grayish white
Streak
White
Tenacity
brittle
Cleavage
None Observed
Fracture
Irregular/Uneven

Optical

Optical type
Biaxial (-)
Pleochroism
Non-pleochroic
UV response
None

Crystallography

Crystal system
Monoclinic
Space group
P21/c
Cell parameters
a = 3.5485(12) Å · b = 6.352(2) Å · c = 19.254(6) Å
Cell angles
β = 92.393(13) °
Ratio a:b:c
1 : 1.790 : 5.426
Z
4
Type-locality form

Shimazakiite forms aggregates up to 3 mm where shimazakiite-4M tends to occur in nanometer-sized twin lamellae and shimazakiite-4O in micrometer-sized lamellae.

Crystal structure

Chemical composition

Constituent elements
Mass composition breakdown
ElementAtoms At. mass g/mol Mass g/molMass share
20CaCalciumCalcium240.07880.156
44.10%
8OOxygenOxygen515.99979.995
44.01%
5BBoronBoron210.81021.620
11.89%
Total181.771100.00%

Mass share = atoms × atomic mass ÷ molar mass × 100

From IMA formula

Synonyms

  • IMA2010-085a
  • Shimazakiiet

In other languages

German
IMA 2010-085a · Shimazakiit
Italian
shimazakiite
Japanese
島崎石

Classification

Strunz
10th ed.

6.BC.25

  • 6BoratesClass
  • 6.BDiboratesDivision
  • 6.BCIno-diborates with triangles and/or tetrahedraGroup
  • 6.BC.25ShimazakiiteSpecies

Literature, links & citation

Citations
  1. 2011Williams, P. A., Hatert, F., Pasero, M., Mills, S. J. (2011) New minerals and nomenclature modifications approved in 2011, CNMNC Newsletter No. 10. Mineralogical Magazine, 75 (5) 2549-2561 doi:10.1180/minmag.2011.075.5.2549 DOI: 10.1180/minmag.2011.075.5.2549
  2. 2013Kusachi, I., Kobayashi, S., Takechi, Y., Nakamuta, Y., Nagase, T., Yokoyama, K., Momma, K., Miyawaki, R., Shigeoka, M., Matsubara, S. (2013) Shimazakiite-4M and shimazakiite-4O, Ca2B2O5, two polytypes of a new mineral from Fuka, Okayama Prefecture, Japan. Mineralogical Magazine, 77 (1) 93-105 doi:10.1180/minmag.2013.077.1.09 DOI: 10.1180/minmag.2013.077.1.09
  3. 2016(2016) Shimazakiite. Handbook of Mineralogy. Mineralogical Society of America
Cite this entry
@misc{mineral2026,
  author    = {Mineral Index editorial board},
  title     = {Shimazakiite — Mineral Index},
  year      = {2026},
  url       = {https://mineralindex.org/minerals/shimazakiite-41969},
  note      = {Accessed 2026-05-11}
}