GEM KNOWLEDGE · LABORATORY NOTES
Charoite
Charoite and its Russian home
Charoite is a rare silicate mineral known for flowing lilac-to-purple patterns. Published mineralogical research places its distinctive occurrence in the Murun Massif of Yakutia, Russia. Its rarity reflects this exceptionally restricted geological source.
The polished material can be a charoite-rich rock, called charoitite, with several companion minerals. Its light, dark and purple areas need not all be the same mineral. Our laboratory findings below document the particular accessories identified in the submitted sphere.
Lacalamita et al., “Micro-FTIR and EPMA Characterisation of Charoite from Murun Massif (Russia)” (2018) describes the mineral’s unique Russian occurrence and complex silicate structure.
A purple sphere was examined to identify its principal and accessory minerals.
Finding: Sample 92936 (#11), completed August 10, 2022, is mainly charoite. The examined areas also contained an apatite-group mineral, aegirine-augite, aegirine and a calcium-rich mica such as margarite.
The report describes this as a rare metasomatic rock associated with contact between syenite and limestone in the Chara River region of southwestern Yakutia. Tinaksite and several other possible accessory minerals were not found or exposed on the surfaces examined. That observation does not rule out their presence elsewhere in the rock.
View the original report
Select a page to enlarge it. 5 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 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 spectral analysis of spot 1 in Fig. 2 (Apatite group)
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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 (charoite)
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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. 5: Backscattered electron image of another 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. 6: Energy dispersive spectral analysis of spot 1 in Fig. 5 (a calcium-rich mica such as margarite)
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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. 7: Backscattered electron image of another 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. 8: Energy dispersive spectral analysis of spot 1 in Fig. 7 (aegirine-augite)
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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. 9: Energy dispersive spectral analysis of spot 2 in Fig. 7 (aegirine
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: 92936 (#11, charoite sphere)
Submitted by: K. Bitner
Date submitted: July 14, 2022.
Date completed: August 10, 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. A Bruker D2 Phaser X-ray diffractometer was used and operated at 30 kV and 10 mA.
Fig. 1: Photograph of the specimen. 2.8 cm maximum dimensions.
2211
Fig. 2: Backscattered electron image of an area of the specimen.
Fig. 3: Energy dispersive spectral analysis of spot 1 in Fig. 2 (Apatite group)
Fig. 4: Energy dispersive spectral analysis of spot 2 in Fig. 2 (charoite)
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Fig. 5: Backscattered electron image of another area of the specimen.
Fig. 6: Energy dispersive spectral analysis of spot 1 in Fig. 5 (a calcium-rich mica such as margarite)
Fig. 7: Backscattered electron image of another area of the specimen.
Fig. 8: Energy dispersive spectral analysis of spot 1 in Fig. 7 (aegirine-augite)
Fig. 9: Energy dispersive spectral analysis of spot 2 in Fig. 7 (aegirine
Table 1: Minor and trace element composition of the specimen. (in wt. %).
| Element | Reported value |
|---|---|
| Barium | 0.77 |
| Calcium | 15.6 |
| Iron | 0.02 |
| Manganese | 0.05 |
| Phosphorus | 0.2 |
| Potassium | 8.9 |
| Silicon | 26.8 |
| Sodium | 2.6 |
| Strontium | 0.7 |
Summary of findings: This specimen (Fig. 1) is mainly made up of charoite (Figs. 2 and 4) which is a very rare mineral! This location (Chara River area, SW Yakutia) is currently not producing material anymore. A lot of accessory minerals have been reported from the site and in this very specimen, an apatite group member (Figs 2 and 3), aegirine-augite (Figs 7 and 8), aegirine (Figs 7 and 9) as well as a calcium-rich mica mineral such as margarite (Figs. 5 and 6) were identified. I was looking for tinaksite, miserite, ferdorite and others but in this specific example they did not happen to be present or to be exposed at the surface where they could be identified.
This is a fabulous example of a rare metasomatic rock which formed at the contact area between a syenite and limestone.
Date: Aug. 10, 2022 Signature
A statement tower from our collection
