GEM KNOWLEDGE · LABORATORY NOTES
Belomerite (Russia)
A luminous feldspar sold as Russian Belomerite or Belomorite.
What the report found: The tested specimen is essentially albite with minor anorthite component. It shows schiller from subtle compositional banding and is described in the report as albite peristerite.
The report finds insufficient potassium for orthoclase or anorthoclase. It therefore does not identify this specimen as conventional potassium-feldspar moonstone. A locality can contain more than one feldspar variety; these findings describe the tested piece.
Related entries: Moonstone (Russia) · Albite (Russia)
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Transcript of the original analytical report, including figure descriptions and findings.
Analytical Result Report Sample id: 9246 (Russian Belomorite) Submitted by: K. Bitner Date submitted: Jan. 15, 2021 Date completed: Jan. 22, 2021 Operating conditions: JEOL JSM-6400 operated at 25 kV acceleration potential, 15 mm working distance, 15 degrees sample tilt, coated with 250 Å carbon. Using the X-ray fluorescence attachment with 35kv potental in conjunction with the EDS system. Fig. 1: Photograph of the specimen, approximately 3.7x3.2x0.5 cm. Fig. 2: Photograph of the specimen with lighting to show iridescence Table 1: Compositions of the specimen (In weight percent) element Silicon dioxide 67.5 Aluminum oxide 20.41 Calcium oxide 0.85 Potassium oxide 0.37 Sodium oxide Ca. 10 Manganese oxide 0.02 Iron oxide 0.01 Summary of findings: This specimen is essentially albite with minor anorthite content (Fig. 1 and Table 1). It does exhibit some schiller effect (Fig. 2). Compositionally, it does not have sufficient to make it a potassium feldspar/orthoclase and there it is not a true moonstone. The potassium content also insufficient to make it an anorthoclase, a sodium-potassium feldspar that often exhibits striking schiller effects. The specimen is a albite with schiller effect, an albite peristerite as it is often called. The schiller is a result of compositionally slightly different bands from which the schiller emerges. A location that produces material like this may also potentially produce true orthoclase or anorthoclase as deposits are generally somewhat heterogenous. Date: January 22, 2021 Signature