GEM KNOWLEDGE · LABORATORY NOTES
Dolomite Marble
A banded specimen identified as dolomite marble, previously cataloged as Mystery Stone 2. The laboratory found mainly dolomite with minor potassium feldspar.
Finding: Sample 92837 (#7), completed September 7, 2021, is mainly dolomite with minor potassium feldspar. The researcher described banded dolomite marble and noted a visual resemblance to some stromatolitic dolomite marble.
Interpretation limits: Resemblance does not prove a stromatolite or a Michigan locality for this specimen. The feldspar could reflect original clastic grains or later formation from precursor material; the report leaves that question open.
View the original report
Select a page to enlarge it. 3 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.
See also Mystery Stone 1 (Brazil), a different specimen and report.
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.
-
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 the specimen.
-
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. (dolomite)
-
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. (potassium feldspar)
-
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. 6: X-ray map of Fig. 2. Left: silicon: orange, potassium: green. Right: iron: blue
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: 92837 (#7)
Submitted by: K. Bitner
Date submitted: Aug.2, 2021.
Date completed: Sept. 7, 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 35 kV potential in conjunction with the EDS system.
Fig. 1: Photograph of the specimen. 4.4 cm maximum dimension.
Fig. 2: Backscattered electron images of the specimen.
Fig. 3: Energy dispersive spectral analysis of spot 1 in Fig. 2. (dolomite)
Fig. 4: Energy dispersive spectral analysis of spot 2 in Fig. 2. (potassium feldspar)
NaNa
Fig. 6: X-ray map of Fig. 2. Left: silicon: orange, potassium: green. Right: iron: blue
Table 1: Minor and trace element composition of the specimen. (in wt. %).
| Element | Reported value |
|---|---|
| Iron | 0.59 |
| Aluminum | 1.22 |
| Phosphorus | 0.08 |
| Titanium | 0.03 |
| Manganese | 0.01 |
Summary of findings: This specimen (Fig. 1) is mainly composed of dolomite (Figs. 2, 3 and 5) with minor amounts of potassium feldspar (Figs. 2, 4, and 5). It is a banded dolomite marble that bears a strong resemblance to some stromatolitic dolomite marble I know from Michigan, the Proterozoic dolomite which was deposited as algal and microbial mats. These stromatolites have been found in many places worldwide and they can look very similar in many locations. The contribution of feldspars is either clastic from the original sediment or it could be authigenic, derived from precursor minerals such as clay and sea water.
Date: Sept. 7, 2021 Signature