What question did this study set out to answer?

The aim is to clarify the misidentification of minerals in the Leinster Granite, particularly focusing on unusual zircons thought to be present.

March 6, 2026

‘Unusual Zircons From the Leinster Pluton’ Are Sillimanite

Key Points

The aim is to clarify the misidentification of minerals in the Leinster Granite, particularly focusing on unusual zircons thought to be present.
Re-examination of morphological features of minerals in the Leinster Granite.
Analysis of mineral content using chemical techniques.
Application of both rock crushing and acid digestion methods for mineral extraction.
Identified minerals originally categorized as zircons are reclassified as sillimanite.
Confirmed that sillimanite appears as inclusions within muscovite phenocrysts.
Demonstrated that the original extraction technique contributed to the misidentification of minerals.

Abstract

‘Unusual zircons’ with exceptionally high elongation ratios were reported from the porphyritic muscovite Type III variety of the peraluminous Leinster Granite of SE Ireland in a 1973 Mineralogical Magazine paper by L.N. Gupta. However, observations and analyses of these ‘zircons’ reveal them to be sillimanites. Gupta had originally used an acid digestion technique, rather than rock crushing, to extract zircons for morphological—but not chemical—analysis. As a result, hitherto unrecognised sillimanite (originally presumed to be zircons) were liberated from within what is now known to be magmatically zoned muscovite. In this paragenesis, sillimanite occurs as epi/topotaxial inclusions within a subset of the Leinster Granite muscovite phenocrysts.

Bookmark

‘Unusual Zircons From the Leinster Pluton’ Are Sillimanite

Key Points

Abstract

Cite This Study