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Malachite: Crystal structure | Sample photo | Raman spectrum | Interpretation | References

Crystal structure of Malachite

Formula:

Cu2(CO3)(OH)2

Crystal Data:

Crystal System: Monoclinic - Prismatic

Point Group: 2/m

Cell Data:

Space Group: P21/a, a = 9.502, b = 11.974, c = 3.24, Z = 4

Using the mouse (click here for more information)

Density (calc.) = 4.03 and V = 364.35 Å3
Element color: Cu, C, O, H
Malachite sample
Azurite

Sample no. 5393 from the "Mineralogy and Petrography Museum Grigore Cobălcescu" of "Alexandru Ioan Cuza" University, Iaşi.

Origin: Eisenzeche - Germany.




Click image to enlarge
Raman spectrum and vibrations of Malachite
Element color: C, O Toggle Grid Toggle Coordinates Reverse Spectrum

Click to in the Raman spectrum. To see the vibrations click on one of them (highlight region) and it (the selected vibration) will appear on the right side of the Raman spectrum.
Below spectra are various settings, and other vibrations of malachite (which are not present in this spectrum).
You have the possibility to zoom in the spectrum by selecting a spectral region you need to be increased (along axis x); to zoom keep the left mouse-click continously pressed, drag (to left or to right) and release the left button. To return to the initial size spectrum, press the right click on the spectrum -> Zoom -> Reset View.
Model type:
Sticks Ball-and-Sticks (1) Ball-and-Sticks (2) CPK (Spacefill)

Orientation:
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Spin on Spin off
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CO3 polyhedra on CO3 polyhedra off 		Vibrations:
ν4b (E') ν4a (E') ν2 (A"2) ν1 (A'1) ν3a (E') ν3b (E')

Vibration on Vibration off 		Download spectrum:
Raman spectrum .txt Raman spectrum .spc


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Interpretation of Raman spectrum of Malachite

Malachite has two characteristic very strong bands at 435 and 1495 cm-1.

As in the case of azurite, the bands at the lowest region of the spectrum of malachite can be attributed to the lattice modes. In this region the spectrum shows an intense band at 434 cm-1, and the others at: 215, 269, 354, 536 and 596 cm-1.

The characteristic bands for CO3 group are observed at: 1059 and 1097 cm-1 for the ν1 symmetric stretching modes (of two different CO3 groups - doubly degenerate mode); 820 cm-1 attributed to ν2 asymmetric bending (Frost et al., 2002); 1368, 1462 and 1495 cm-1 assigned to ν3 asymmetric stretching mode; and for ν4 symmetric bending mode (doubly degenerate mode) at 722 and 755 cm-1. For the hydroxyl-stretching region, the spectrum shows bands at 3310 and 3382 cm-1. The vibration mode of hydroxyl group (O-H bending mode) appear at 1639 cm-1.

Differences between the spectra of malachite and azurite may be explained by the molecular structure of azurite being based upon a distorted square planar arrangement compared with a distorted octahedral arrangement about the copper in malachite (Frost et. al., 2002).


Buzgar et al., 20091 Frost et al., 2002 Mattei et al., 2008 Assignment
215, 269, 354,
434, 536, 596		 130, 142, 151, 166,
176, 205, 217, 267,
294, 320, 349, 389,
429, 514, 531, 563,
596		 157, 171, 182, 204,
224, 272, 352, 435,
513, 537, 601		 T(Cu,CO3)
722, 755 718, 750 723, 753 ν4 symmetric CO3 deformation
820 807, 817   ν2 asymmetric CO3 deformation
1059, 1097 1098 1058, 1101 ν1 symmetric CO3 stretching
1368, 1462, 1495 1365, 1423, 1493, 1514 1370, 1463, 1497 ν3 asymmetric CO3 stretching
1639 O-H bending mode
3310, 3382 3349, 3380 3380 O-H stretching mode
NO = not observed
References

• The Mineralogy Database [link]

• Crystal data (.cif file) from the American Mineralogist Crystal Structure Database [link]

• 1BUZGAR N., APOPEI A. I. (2009) - The Raman study on certain carbonates. Analele Stiintifice ale Universitatii “Al. I. Cuza” - Iasi, Tome 55, issue 2, 97-112 [link]

• FROST R. L., MARTENS W. N., RINTOUL L., MAHMUTAGIC E., KLOPROGGE J. T. (2002) - Raman spectroscopic study of azurite and malachite at 298 and 77 K. Journal of Raman Spectroscopy, 33, p. 252-259 [link]

• MATTEI E., VIVO G., SANTIS A., GAETANI C., PELOSI C., SANTAMARIA U. (2008) - Raman spectroscopic analysis of azurite blackening. Journal of Raman Spectroscopy, 39, p. 302-306 [link]