GEM KNOWLEDGE · LABORATORY NOTES
Chocolate Calcite (China)
A specimen from Tonglushan Mine, China, also sold as Sunset Calcite and Chocolate Hematite.
Finding: Sample 10472, completed January 17, 2024, is predominantly calcite. After the first calcite crystals formed, powdery hematite coated them; a later growth of calcite followed.
The dark coating explains the market name, but the bulk of this tested specimen is calcite. See Chocolate Hematite for the same report under its alternate name.
Locality: Tonglushan Mine, China, according to Soul Body Gems provenance. The analytical report identifies the minerals in the submitted specimen; it does not independently verify geographic origin.
See Sunset Calcite for this same tested specimen under its other market name.
View the original report
Select a page to enlarge it. 3 pages; the 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 image of an area of 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 spectrum of spot 1 in Fig. 2 (calcite)
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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 spectrum of spot 1 in Fig. 4 (hematite coating on calcite)
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: 10472 (#11)
Submitted by: Soul Body Gems
Date completed: 1-16-2024
Operating conditions: An AMRAY 1830 SEM operated at 25 kV acceleration potential, 24 mm working distance, 0 degrees sample tilt, coated with 250 Å carbon, and also using the attached XRF unit operated at 30 kV.
A BRUKER Titan X-ray fluorescence spectrometer was also used and operated for 30 seconds at 50, 25, and 10 kV.
Fig. 1: Photograph of the specimen. Approximately 6 cm maximum dimension.
Fig.2: Backscattered electron image of an area of the specimen.
Fig. 3: Energy dispersive spectrum of spot 1 in Fig. 2 (calcite)
Fig. 4: Energy dispersive spectrum of spot 1 in Fig. 4 (hematite coating on calcite)
Table 1: minor and trace elements in the calcite.
| Element | Reported value |
|---|---|
| Iron | 0.4 |
| Magnesium | 0.1 |
| Manganese | 0.02 |
| Strontium | 0.01 |
Summary of findings: This specimen (Fig. 1) shows a multi-step crystallization. The bulk of the specimen is calcite (Figs. 2 and 3). After the formation of calcite, a coating of powdery hematite was deposited (Figs. 2 and 4), this was followed by a second growth of calcite as seen in Figs 1 and 2. Table 1 shows that the calcite is low in trace and minor elements, some of the hematite may be due to hematite inclusions in the area analyzed.
Date: January 17. 2024 Signature