Opalized (petrified) wood from Megyaszó, Hungary
- Details
- Created: Tuesday, 24 December 2024 18:58
The slice of opalized wood (Figure 1) is reportedly from Megyaszó, Szerencs District, Borsod-Abaúj-Zemplén County, Hungary, likely from Tetlinke Ditch[1]. It shows three distinct parts, a beige to grayish brown core where the replaced xylem anatomy can be observed (Figure 2 & 3), a black vitreous inner layer and a white outer layer that is fibrous and brittle (fibers are easily released).
The most common petrified wood perimineralizations are silicates (quartz), and in a less extent, oxides, sulfides, carbonates and sulfates, sometimes native elements but more rarely with opal which is an 'amorphous' hydrated sillica softer and less dense than quartz. As a kind of rarity, it is worth to confirm this petrified wood is opalized.
Figure 1. This slice of opalized wood from Megyaszó shows apeculiar pattern with a beige to grayish brown core surrounded by a
first black layer and then a white outer layer. Size: 63 x 41 mm.
| Shape | slice of a trunk or branch section |
| Size | 63 x 41 x 9 mm |
| Color | white, black, beige / brown |
| Diaphaneity | opaque rims / layers (white and black) and translucent core (beige / grayish brown) |
| Lustre | dull (white layer), vitreous (black layer and beige core) |
| Weight | 33 g |
| SG | - |
| RI | - |
| DR | - |
| Pleochroism | - |
| Polariscope / Conoscope | - |
| SWUV | - |
| LWUV | small bright whitish areas in the white outer layer |
| Magnetic susceptibility N52 | inert |
| Chelsea filter | - |
Table 1. Observational and measured properties
Figure 2. Xylem anatomy details showing the tracheids' cross section and a possible vessel section (white circle in upper middle).
Smartphone photography through the occular of the binoccular at 20x.
Figure 3. Xylem anatomy showing almost rectangular tracheids' cross sections. Smartphone photography through the occular of the binoccular
at 20x.
Infrared reflectance spectroscopy:
Due to the relatively large size of the slice, only two areas, the core and the outer layer, were inspected by FTIR that yielded the spectrum shown in Figure 4. The core area which is well polished gave a better spectra than the white outer layer (rough and dull) that was much weaker and noisy. Both of them yielded the same pattern, a pattern that is consistent with opal. For comparison, Figure 5 shows the IR reflectance of a well known colorless hyalite opal from Tarcal, Hungary. Although the determination of opal is certain for the core, it is less obvious for the white outer layer, some fibrous quartz is known to coexist with opal.
Figure 4. The IR reflectance spectrum of the core material of the slice shows a pattern that is consistent with opal, it can be compared to another spectrum of an opal from Hungary (see below in Figure 5).
Figure 5. IR reflectance spectrum of colorless hyalite opal from Tarcal, Hungary.Raman spectroscopy:
Raman spectra could not be collected with a 636 nm laser because of the light scattering in the material that dazzled the spectroscope.
UV-VIS-NIR spectroscopy:
Not investigated.
Photoluminescence spectroscopy:
Not investigated although the small bright whitish areas in the white outer layer while exposed to the 365 nm UV.
Conclusion:
The petrified woods found in Tetlinke Ditch near Megyaszó are opalized woods as confirmed by FTIR. Further investigations have to be conducted to determine whether the white outer layer is fibrous quartz or a kind of fibrous opal.
[1] Petrified Wood from Tetlinke Ditch, Megyaszó, Szerencs District, Borsod-Abaúj-Zemplén County, Hungary, December 2024, Mindat. https://www.mindat.org/locentry-296861.html