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Loomisite
A valid IMA mineral species
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About Loomisite
Tom Loomis
Formula:
Ba[Be2P2O8] · H2O
Colour:
White
Lustre:
Vitreous, Silky
Hardness:
3½ - 4
Specific Gravity:
3.46
Crystal System:
Monoclinic
Member of:
Name:
Named after Tom Loomis, mineral collector and dealer from South Dakota, USA, who collected the type material.
Chemically related to minjiangite that may be treated as its anhydrous counterpart. Both are beryllophosphates.
Loomisite is the first natural example with the zeolite ABW-type framework, which is adopted by over 100 synthetic compounds with different chemical compositions.
Loomisite is the first natural example with the zeolite ABW-type framework, which is adopted by over 100 synthetic compounds with different chemical compositions.
Unique Identifiers
Mindat ID:
56033
Long-form identifier:
mindat:1:1:56033:1
Similar Names
| Lamosite | A synonym of 'Lamalginite' |
IMA Classification of Loomisite
Approved
IMA Formula:
Ba[Be2P2O8]·H2O
Approval year:
2022
First published:
2023
Type description reference:
Classification of Loomisite
8.DN.
8 : PHOSPHATES, ARSENATES, VANADATES
D : Phosphates, etc. with additional anions, with H2O
N : With only large cations
8 : PHOSPHATES, ARSENATES, VANADATES
D : Phosphates, etc. with additional anions, with H2O
N : With only large cations
Mineral Symbols
As of 2021 there are now IMA–CNMNC approved mineral symbols (abbreviations) for each mineral species, useful for tables and diagrams.
| Symbol | Source | Reference for Standard |
|---|---|---|
| Lmi | IMA–CNMNC | Warr, L.N. (2021). IMA–CNMNC approved mineral symbols. Mineralogical Magazine, 85(3), 291-320. doi:10.1180/mgm.2021.43 |
Physical Properties of Loomisite
Vitreous, Silky
Transparency:
Transparent
Colour:
White
Streak:
White
Hardness:
3½ - 4 on Mohs scale
Tenacity:
Brittle
Cleavage:
Perfect
{100} and {110}.
{100} and {110}.
Parting:
None
Density:
3.46(5) g/cm3 (Measured) 3.512 g/cm3 (Calculated)
Optical Data of Loomisite
Type:
Biaxial (+)
RI values:
nα = 1.579(5) nβ = 1.591(5) nγ = 1.606(5)
2V:
Measured: 82° (2), Calculated: 85°
Max. Birefringence:
δ = 0.027
Based on recorded range of RI values above.
Based on recorded range of RI values above.
Interference Colours:
The colours simulate birefringence patterns seen in thin section under crossed polars. They do not take into account mineral colouration or opacity.
Michel-Levy Bar The default colours simulate the birefringence range for a 30 µm thin-section thickness. Adjust the slider to simulate a different thickness.
Grain Simulation You can rotate the grain simulation to show how this range might look as you rotated a sample under crossed polars. Each grain retains its interference colour (retardation) while its brightness falls to black at extinction and reaches a maximum between extinction positions.
The colours simulate birefringence patterns seen in thin section under crossed polars. They do not take into account mineral colouration or opacity.
Michel-Levy Bar The default colours simulate the birefringence range for a 30 µm thin-section thickness. Adjust the slider to simulate a different thickness.
Grain Simulation You can rotate the grain simulation to show how this range might look as you rotated a sample under crossed polars. Each grain retains its interference colour (retardation) while its brightness falls to black at extinction and reaches a maximum between extinction positions.
Surface Relief:
Moderate (positive)
Relative to Canada balsam mounting medium (n ≈ 1.537).
Relative to Canada balsam mounting medium (n ≈ 1.537).
This shows the grain boundary and Becke line effect under plane-polarised
light, based on the contrast between this mineral's average refractive
index and the mounting medium. It does not take into account mineral
colouration.
In focus
Interference Figure:
This shows the idealized biaxial acute bisectrix (Bxa) interference figure
- the conoscopic view for a grain cut perpendicular to the acute bisectrix, using
this mineral's 2V. The two small white dots mark the melatopes - the points
where the two optic axes emerge - and are shown only when they fall within the
field of view. The coloured bands are isochromatics, and the dark bands are
isogyres.
Rotate the stage: at 0°/90° the isogyres form a cross through the melatopes; at 45° they pull apart into curved hyperbolas. That splitting on rotation - absent in a uniaxial figure - is the standard diagnostic test for telling biaxial minerals from uniaxial ones. If 2V is large, the melatopes may fall outside the field of view, as they often do at the microscope too.
Rotate the stage: at 0°/90° the isogyres form a cross through the melatopes; at 45° they pull apart into curved hyperbolas. That splitting on rotation - absent in a uniaxial figure - is the standard diagnostic test for telling biaxial minerals from uniaxial ones. If 2V is large, the melatopes may fall outside the field of view, as they often do at the microscope too.
Dispersion:
very weak with r > v
Pleochroism:
Non-pleochroic
Chemistry of Loomisite
Mindat Formula:
Ba[Be2P2O8] · H2O
Element Weights:
Crystallography of Loomisite
Crystal System:
Monoclinic
Class (H-M):
m - Domatic
Cell Parameters:
a = 7.629(2) Å, b = 9.429(2) Å, c = 4.762(1) Å
β = 91.272(5)°
β = 91.272(5)°
Ratio:
a:b:c = 0.809 : 1 : 0.505
Unit Cell V:
342.46 ų (Calculated from Unit Cell)
Z:
2
Morphology:
Divergent sprays of very thin bladed crystals with a tapered termination.
Twinning:
Pervasively twinned on (100) with the twin law [1 0 0 / 0 -1 0 / 0 0 -1] or consist of multi-crystal intergrowth.
Comment:
Space group Pn
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 4.259 Å | (39) |
| 3.813 Å | (29) |
| 3.068 Å | (44) |
| 2.897 Å | (100) |
| 2.869 Å | (65) |
| 2.816 Å | (54) |
| 2.385 Å | (58) |
| 2.045 Å | (35) |
Type Occurrence of Loomisite
General Appearance of Type Material:
Divergent sprays of very thin bladed crystals that gently taper to a blunt termination. Individual crystals are found up to 0.80 x 0.06 x 0.03 mm.
Place of Conservation of Type Material:
Type material is deposited in the collections of the University of Arizona Alfie Norville Gem and Mineral Museum, 15 N Church Ave, Tucson, AZ 85701, USA, catalogue no. 22710 (holotype), and the RRUFF Project, deposition no. R210017 (cotype).
Geological Setting of Type Material:
Granite pegmatite.
Associated Minerals at Type Locality:
Synonyms of Loomisite
Other Language Names for Loomisite
Relationship of Loomisite to other Species
Member of:
Other Members of Zeolite Group:
| Alflarsenite | NaCa2Be3Si4O13(OH) · 2H2O | Mon. 2 : P21 |
| Amicite | K2Na2Al4Si4O16 · 5H2O | Mon. 2 |
| Ammonioleucite | (NH4)(AlSi2O6) | Tet. 4/m : I41/a |
| Analcime | Na(AlSi2O6) · H2O | Tric. 1 : P1 |
| Arzamastsevite | K6Al5Si6O20(OH)4Cl | Tet. 42m : I42m |
| Bellbergite | (K,Ba,Sr)2Sr2Ca2(Ca,Na)4[Al3Si3O12]6 · 30H2O | Hex. |
| Bikitaite | LiAlSi2O6 · H2O | Tric. 1 : P1 |
| Boggsite | Ca8Na3(Si,Al)96O192 · 70H2O | Orth. mmm(2/m2/m2/m) : Imma |
| Brewsterite Subgroup | Zeolite Group. | |
| Chabazite-Levyne Subgroup | M[Al2Si4O12] · 6H2O | |
| Chiavennite | CaMnBe2Si5O13(OH)2 · 2H2O | Mon. 2/m : P21/c |
| Clinoptilolite Subgroup | (Na/Ca/K)3-6[Al6-7Si29-30O72] · 20H2O | |
| Cowlesite | CaAl2Si3O10 · 6H2O | Orth. mmm(2/m2/m2/m) |
Big Chief Mine, Glendale, Keystone Mining District, Pennington County, South Dakota, USA