Grimaldiite Mineral Data

General Grimaldiite Information

Chemical Formula:

Cr+++O(OH)

Composition:

Molecular Weight = 85.00 gm

Chromium 61.17 % Cr 89.40 % Cr₂O₃

Hydrogen 1.19 % H 10.60 % H₂O

Oxygen 37.64 % O

______ ______

100.00 % 100.00 % = TOTAL OXIDE

Empirical Formula:

CrO(OH)

Environment:

Fine-grained intergrowth with other chromium oxide-hydroxide minerals in alluvial gravels. Trimorphous with bracewellite and guyanaite.

IMA Status:

Approved IMA 1967

Locality:

Basin of the Merume River, Guyana. Link to MinDat.org Location Data.

Name Origin:

Named for Frank Saverio Grimaldi (1915- ), formerly Chief Chemist, U.S. Geological Survey.

Name Pronunciation:

Grimaldiite + Pronunciation

Grimaldiite Image

Images:

Grimaldiite

Comments: Grimaldiite, variety merumite, stream rounded crystalline grains.
Location: Merume River, Mazaruni-Potaro District, Guyana. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

Grimaldiite Crystallography

Axial Ratios:

a:c = 1:4.50454

Cell Dimensions:

a = 2.973, c = 13.392, Z = 3; V = 102.51 Den(Calc)= 4.13

Crystal System:

Trigonal - Hexagonal Scalenohedral H-M Symbol (3 2/m) Space Group: R 3m

$Help on X Ray Diffraction:$ X Ray Diffraction:

By Intensity(I/I_o): 4.44(1), 2.407(0.3), 1.858(0.25),

Physical Properties of Grimaldiite

Color:

Dark red, Reddish brown.

Density:

4.11

Diaphaneity:

Opaque

Hardness:

3.5-4.5 - Between Copper Penny and Fluorite-Apatite

Luster:

Metallic

Streak:

red

Optical Properties of Grimaldiite

Optical Data:

NCalc= 2.22 - from Gladstone-Dale relationship (KC = 0.2953) where Ncalc=Dcalc*KC+1
NCalc= 2.21 - from Gladstone-Dale relationship (KC = 0.2953) where Ncalc=Dmeas*KC+1

Calculated Properties of Grimaldiite

Electron Density:

Bulk Density (Electron Density)=3.98 gm/cc
note: Specific Gravity of Grimaldiite =4.13 gm/cc.

Fermion Index:

Fermion Index = 0.05
Boson Index = 0.95

Photoelectric:

PE_Grimaldiite= 13.79 barns/electron
U=PE_Grimaldiite x rElectron Density= 54.95 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)
Grimaldiite is Not Radioactive

Grimaldiite Classification

Dana Class:

06.01.05.01 (06)Hydroxides and Oxides Containing Hydroxyl

(06.01)where X+++O OH

(06.01.05)Dana Group

06.01.05.01 Grimaldiite CrO(OH) R 3m 3 2/m

Strunz Class:

04.FE.20 04 - OXIDES (Hydroxides, V[5,6] vanadates, arsenites, antimonites, bismuthites, sulfites, selenites, tellurites, iodate

04.F - Hydroxides (without V or U)

04.FE -Hydroxides with OH, without H2O; sheets of edge-sharing octahedra

04.FE.20 Grimaldiite CrO(OH) R 3m 3 2/m

04.FE.20 Heterogenite-2H CoO(OH) P 6₃/mmc 6/m 2/m 2/m

04.FE.20 Heterogenite-3R CoO(OH) R 3m 3 2/m

Other Grimaldiite Information

References:

NAME( AntBidBlaNic3) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990)

See Also:

Links to other databases for Grimaldiite :
1 - Am. Min. Crystal Structure Database
2 - Athena
3 - EUROmin Project
4 - Ecole des Mines de Paris
5 - GeoScienceWorld
6 - Google Images
7 - Google Scholar
8 - Handbook of Mineralogy (MinSocAm)
9 - Handbook of Mineralogy (UofA)
10 - MinDAT
11 - Mineralienatlas (Deutsch)
12 - Online Mineral Museum
13 - QUT Mineral Atlas
14 - Ruff.Info

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Print or Cut-and-Paste your Grimaldiite Specimen Label here :

Grimaldiite

Cr+++O(OH)
Dana No: 06.01.05.01 Strunz No: 04.FE.20
Locality:

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