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Eight-membered cyclosilicate rings in muirite.
Science (New York, N.Y.)
|September 3, 1971
Summary
The crystal structure of muirite reveals rare eight-membered silicate rings, challenging previous assumptions about their stability in minerals. This discovery offers new insights into silicate mineralogy and crystal chemistry.
Area of Science:
- Mineralogy
- Crystallography
- Geochemistry
Background:
- Muirite is a complex barium silicate mineral with the formula Ba(10)(Ca,Mn,Ti)(4)Si(8)O(24)(Cl,OH,O)(12) . 4H(2)O.
- Silicate anions are fundamental building blocks in minerals, with ring structures being common.
- Previous research suggested that eight-membered silicate rings are energetically less stable than six-membered rings.
Purpose of the Study:
- To determine the crystal structure of muirite.
- To investigate the nature of silicate anions present in muirite.
- To assess the significance of the observed silicate ring structure in the context of silicate mineral stability.
Main Methods:
- Single-crystal X-ray diffraction was used to elucidate the crystal structure of muirite.
- Detailed crystallographic analysis was performed to identify and characterize the silicate anions.
- Thermodynamic principles were considered to evaluate the stability of the observed ring structures.
Main Results:
- The crystal structure determination of muirite confirmed the presence of discrete cyclic silicate anions.
- These anions are eight-membered rings, represented as (Si(8)O(24))(16-), formed by the condensation of eight silicate tetrahedra.
- This represents the first reported occurrence of eight-membered silicate rings in a mineral.
Conclusions:
- The discovery of eight-membered silicate rings in muirite provides novel structural information in mineralogy.
- The energetic stability of these eight-membered rings warrants further investigation, potentially revising current understanding.
- Muirite's structure offers a unique case study for understanding silicate condensation and stability in geological contexts.
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