GEM KNOWLEDGE · LABORATORY NOTES
Blue Obsidian — Tested Market Name
A blue thumb stone sold as “Blue Obsidian” was analyzed to determine whether it was natural volcanic glass.
Finding: Sample 92904 (#3), completed April 15, 2022, was interpreted by the laboratory as man-made material, predominantly sodium-rich glassy silicate with some crystalline sodium-calcium-aluminum silicate. It is not natural obsidian.
Cobalt was detected as a possible contributor to the blue color, perhaps aided by iron and chromium. The report found no removable dye by solvent testing. A product can be blue throughout and still be manufactured glass; color alone is not proof of natural origin.
View the original report
Select a page to enlarge it. 4 pages; findings are summarized in accessible text above.
Report images © Soul Body Gems, Alexander Falster and the Maine Mineral & Gem Museum. Please acknowledge all three when referring to these results. Findings apply to the specimen examined.
Understanding the report figures
Use this guide alongside the written findings and the original report transcript. It explains the purpose of each analytical figure and preserves the laboratory’s own figure labels. The interpretations apply to the tested specimen; signals alone do not establish the identity of every similar-looking stone.
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Electron microscope image: This view shows small-scale regions selected for analysis. Its brightness contrast helps distinguish regions with different compositions; it is not a photograph of their natural colors. Numbered spots connect this view to the analyses listed in the report.
Laboratory figure caption: Fig. 2: Backscattered electron images of two areas the specimen.
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Elemental spectrum: The peaks record characteristic X-ray signals from elements in the analyzed spot or area. This is an analysis of that location, not automatically of the entire specimen. Any mineral identification or uncertainty named in the laboratory caption is retained below.
Laboratory figure caption: Fig. 3: Energy dispersive spectral analysis of spot 1 in Fig. 2 (sodium calcium aluminum silicate)
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Elemental spectrum: The peaks record characteristic X-ray signals from elements in the analyzed spot or area. This is an analysis of that location, not automatically of the entire specimen. Any mineral identification or uncertainty named in the laboratory caption is retained below.
Laboratory figure caption: Fig. 4: Energy dispersive spectral analysis of spot 2 in Fig. 2. (sodium-rich glass
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Element map: This map shows where the named elements occur within the analyzed area. Its colors represent the laboratory’s selected element channels, rather than the specimen’s visible colors. The caption below preserves any color key or distribution noted by the laboratory.
Laboratory figure caption: Fig. 5: X-ray map of the area shown in Fig. 2: Sodium: yellow, calcium: red.
Read the original laboratory report as text
The following text and tables are transcribed from the original laboratory document. Figure captions identify the report images; the laboratory interpretations and limitations are preserved.
Laboratory report 1
Analytical Result Report
Sample id: 92904 (#3) blue thumb stone
Submitted by: K. Bitner
Date submitted: April 15, 2022.
Date completed: April 115, 2022.
Operating conditions: An AMRAY 1830 SEM operated at 25 kV acceleration potential, 26 mm working distance, 15 degrees sample tilt, coated with 250 Å carbon. Using the X-ray fluorescence attachment with 35 kV potential in conjunction with the EDS system.
Fig. 1: Photograph of the specimen. 5.5 cm maximum dimensions. Right: close-uo showing diverging needles.
Fig. 2: Backscattered electron images of two areas the specimen.
Fig. 3: Energy dispersive spectral analysis of spot 1 in Fig. 2 (sodium calcium aluminum silicate)
Fig. 4: Energy dispersive spectral analysis of spot 2 in Fig. 2. (sodium-rich glass
Fig. 5: X-ray map of the area shown in Fig. 2: Sodium: yellow, calcium: red.
Fig. 6: Petrographic images: plane polarized light on the left, crossed Nichols on the right.
Table 1: Minor and trace element composition of the specimen. (in wt. %).
| Element | Reported value |
|---|---|
| Calcium | 5.10 |
| Chromium | 0.05 |
| Cobalt | 0.10 |
| Iron | 0.30 |
| Manganese | 0.02 |
| Sodium | 6.70 |
Summary of findings: This specimen (Fig. 1) is unusual. Some radiating fibers (Fig. 1) can be seen microscopically and in backscattered electron mode, elongate crystals are seen which tend to line up in en echelon rows (Fig. 2). These crystals are composed of a sodium calcium aluminum silicate (Figs. 2 and 3). The bulk material is a sodium rich aluminum silicate material with very high silicon content. The aluminum content is not very high, no more than 5 wt. %. An X-ray map shows elevated calcium along linear trends (Fig. 5). Under polarized light, glassy particles are the high sodium silicate materials whereas the birefringent parts are the sodium calcium silicate (Fig. 6). Thus, the sodium calcium silicate is crystalline whereas the sodium-rich silicate is a glassy material. The trace element composition (Table 1) shows cobalt as a potential blue chromophore, possibly aided by the presence of iron and chromium. I believe this is man-made material, dominantly glassy with some crystalline components. It is not dyed, nothing can be extracted with solvents.
Date: April 15, 2022 Signature