Gemological characteristics and inclusions of green rutilated quartz from Huanggangliang, Inner Mongolia

Our plain-English summary of Gemological characteristics and inclusions of green rutilated quartz from Huanggangliang, Inner Mongolia, by S. Zhao, T. Li, Q. Guo, et al (RSC Advances, 2024).

The study

• Authors: S. Zhao, T. Li, Q. Guo, L. Liu, Y. Rao, L. Liao
• Journal: RSC Advances
• Published: 2024;14(5):2896-2904
• Read it: PubMed · Publisher · Free full text

Abstract

Normally, various minerals exist in quartz as inclusions. In this study, methods such as gem microscopy, polarizing microscopy, Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, and electron probe microanalysis (EPMA) were used to systematically study the gemological characteristics and inclusions in green rutilated quartz from Inner Mongolia. Results show that the sample appears green due to the chaotic distribution of green inclusions in the shape of hair filaments. Combined with the chemical composition, the inclusions are Ca-Fe-rich amphiboles with compositions very close to those of the end-member ferro-actinolite. According to the principle of amphibole nomenclature, the inclusions are named ferro-actinolite in the subclass of calc-alkaline amphiboles with a few named ferro-hornblende. Results suggested that the inclusions in green rutilated quartz were formed during the late stage of quartz crystallization. This work provides a new theoretical basis for the study of green rutilated quartz in Huanggangliang, Inner Mongolia.

This journal is © The Royal Society of Chemistry.

In plain English

This was a laboratory mineralogy study, not a health study. It did not examine people, animals or disease, and it did not assess whether the fibrous inclusions it studied were asbestos. The authors examined five samples of green rutilated quartz mined from the Huanggangliang Iron Ore VI Mine in Inner Mongolia, China. They used gem and polarizing microscopes, infrared and Raman spectroscopy, and electron probe microanalysis. Inside the quartz they saw dark green fibrous and needle-shaped (acicular) inclusions scattered with no obvious pattern, which they reported made the quartz look green. Raman spectra identified the inclusions as actinolite. Chemical analysis showed the inclusions were rich in iron. The text gives FeO as 23.485 to 31.832 wt%, but the lowest value in its results table is 26.932 wt%. The authors named the inclusions ferro-actinolite, a calcic amphibole, with a few named ferro-hornblende, and found all were calc-alkaline. Liquid in other small inclusions was identified as water. The authors concluded that the inclusions formed by secondary alteration or metasomatism, and were trapped in the quartz as hydrothermal fluids moved them and temperatures fell.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Laboratory mineralogical and gemological analysis of quartz samples (microscopy, FTIR spectroscopy, Raman spectroscopy, electron probe microanalysis)
• Who was studied: Five green rutilated quartz samples (MGC-1 to MGC-5), 4 to 6 cm long and 2 to 3 cm wide, mined from Huanggangliang Iron Ore VI Mine, Hexigten Banner, Inner Mongolia, China
• Exposure: No human or animal exposure was studied. The material examined was fibrous and acicular green amphibole inclusions inside quartz crystals. The study did not assess whether these inclusions were asbestiform.
• Main results:
  • In the samples, dark green fibrous inclusions were randomly distributed and gave the crystals their green color. Inclusion lengths were printed as 10 to 400 mm and widths as 1 to 10 mm; the unit symbol appears damaged.
  • Raman spectra of the inclusions identified them as actinolite.
  • In electron probe analysis of the inclusions, average SiO2 was 48.529 wt% and average CaO was 11.272 wt%.
  • The text states that FeO in the inclusions ranged from 23.485 to 31.832 wt%, higher than in actinolite and approaching ferro-actinolite (29.4 wt%). The lowest FeO value listed in Table 2 is 26.932 wt% (sample MGC-2), and no value of 23.485 appears there. The article does not explain this discrepancy.
  • By amphibole classification, the inclusions were named ferro-actinolite (calcic amphiboles), with a few named ferro-hornblende.
  • All amphibole inclusions in the samples plotted as calc-alkaline.
  • On a silicon-titanium genesis diagram, the inclusions fell in region V, which the authors describe as a product of secondary alteration or metasomatism.
  • The liquid in gas-liquid inclusions was identified by Raman spectroscopy as water.
• The authors' conclusion: The authors concluded that the green color comes from the many actinolite inclusions, and that the inclusions were formed by secondary alteration or metasomatism and were trapped in quartz during late-stage hydrothermal mineralization.
• Limitations the authors state:
  • The chemical analysis could not measure anions. The authors assumed the roughly 3% shortfall in totals was water.

Topics

Medical terms in this study, explained in our Lexicon: Amphibole Group, End-Member, Ferro-actinolite, amphibole nomenclature, Hornblende.

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