GEM KNOWLEDGE · LABORATORY NOTES
Chocolate Opal / Brown Opal
A brown material sold as “Chocolate Opal” or “Brown Opal” was tested to see what the specimen actually contains.
Tested specimen: 92782 (sample 7) · Report completed: June 22, 2021
Key finding: The laboratory described this tested specimen as essentially quartz with minor calcium, iron, and titanium impurities. Its brown color was attributed to trace iron. It was not identified as opal.
What the report means
The report notes grains and structures resembling ostracod shell fragments. Its suggested origin in a marine or lakeshore setting is an interpretation, not a proven locality or age. The trade name should not be taken as mineral identification.
View the original test results
Select any report page to enlarge it. The pages are reproduced from the analytical report for this individual specimen.
Mineral identification is specific to the sample analyzed. The full report pages preserve the laboratory's wording and limitations.
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 image of sample 7.
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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. ()
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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. 4: X-ray map of the area shown in Fig. 2. Left: Silicvon: red, Calcium green. Right: Calcium green, iron: blue.
Read the report as text
This transcription makes the laboratory findings, figure captions, and table values available without opening the page images. Refer to the original images above for visual details.
Laboratory report
Analytical Result Report Sample id: 92782 (sample 7) Submitted by: K. Bitner Date submitted: June 2, 2021. Date completed: June 22, 2021. 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 35kVpotental in conjunction with the EDS system. Fig. 1: Photograph of the specimens #7, 7 cm maximum dimension of the specimen. Fig. 2: Backscattered electron image of sample 7. Fig. 3: Energy dispersive spectral analysis of spot 1 in Fig. 2. () Fig. 4: X-ray map of the area shown in Fig. 2. Left: Silicvon: red, Calcium green. Right: Calcium green, iron: blue. Table 1: Composition of sample 1. (in wt. %) Silicon 46.31 Calcium 0.13 Iron 0.22 Titanium 0.03 Barium 0.07 Sodium 75 Fig. 5: Photomicrographs of the specimen. Width of field of left image: 5 mm, right image: 1 mm. Note in the right image structures that resemble ostracod shell fragments (arrow). Summary of findings: This specimen (Fig. 1) Is interesting, it is essentially composed of quartz (Figs 2-5, Table 1) with minor impurities of calcium, iron and titanium. Texturally, it is composed of relatively large fragments of brown color (iron in trace amounts is responsible for the color). There are sand sized grains present (Fig. 5 left) and fragments of what looks like ostracod shall fragments (tiny shelled arthropods) (Fig. 5 right). The origin of the specimen may have started out as relatively coarse siliceous clastic material that was deposited in a marine or lacustrine shore environment and was eventually cemented with silica, including the ostracod shells. . Date: June 22, 2021 Signature