GEM KNOWLEDGE · LABORATORY NOTES
Selenite (Mongolia)
A well-formed gypsum crystal from Mongolia, with a small amount of kaolinite clay.
Sample 1135. The header date is March 19, 2025; the signature date is April 19, 2025. Both are retained in the original report.
Gypsum and selenite
Gypsum is the mineral species. Selenite is traditionally used for its transparent crystalline variety; fibrous gypsum is usually called satin spar, while fine-grained massive gypsum is called alabaster. The market often uses “selenite” more broadly, so the words do not always describe precisely the same form.
The analysis identifies gypsum with minor kaolinite. The report also notes monoclinic growth lines, a Mohs hardness of 2 and a slight response to ultraviolet light.
Further reading: Mindat: selenite terminology.
Laboratory 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.
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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. (gypsum)
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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 2 in Fig. 2. (Gypsum with kaolinite)
Read the complete report as text
Analytical Result Report
Sample id: 1135 (#3, Mongolian gypsum)
Submitted by: Soul Body Gems
Date completed: 3-19-2025
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.
Photograph of the specimen. Approximately 7 cm across.
Fig.2: Backscattered electron image of an area of the specimen.
Fig. 3: Energy dispersive spectrum of spot 1 in Fig. 2. (gypsum)
Fig. 4: Energy dispersive spectrum of spot 2 in Fig. 2. (Gypsum with kaolinite)
Summary of findings: This specimen (Fig. 1) is pretty. A well-formed crystal, gypsum it is (Figs. 2 and 3). There is a little kaolinite clay at spot 2. Gypsum forms often in shales which are essentially clay species and clay-sized other minerals.
Fig 2 also shows the growth lines, they are not at 90 degrees, this is typical for gypsum which is monoclinic and its beta angle is non-90 degrees. Additionally, the crystal is scratched by a fingernail, gypsum has a Mohs hardness of 2. And it responds a little to UV light.
Date: 4-19-2025 Signature
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: 1135 (#3, Mongolian gypsum)
Submitted by: Soul Body Gems
Date completed: 3-19-2025
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.
Photograph of the specimen. Approximately 7 cm across.
Fig.2: Backscattered electron image of an area of the specimen.
Fig. 3: Energy dispersive spectrum of spot 1 in Fig. 2. (gypsum)
Fig. 4: Energy dispersive spectrum of spot 2 in Fig. 2. (Gypsum with kaolinite)
Summary of findings: This specimen (Fig. 1) is pretty. A well-formed crystal, gypsum it is (Figs. 2 and 3). There is a little kaolinite clay at spot 2. Gypsum forms often in shales which are essentially clay species and clay-sized other minerals.
Fig 2 also shows the growth lines, they are not at 90 degrees, this is typical for gypsum which is monoclinic and its beta angle is non-90 degrees. Additionally, the crystal is scratched by a fingernail, gypsum has a Mohs hardness of 2. And it responds a little to UV light.
Date: 4-19-2025 Signature