BH250-60b
Title
BH250-60b
Subject
Hauyne Phonolite
Description
Major Minerals: Hauyne, titanaugite, plagioclase, oxides
Optical Properties: Hauyne: Beautiful, fuzzy, bluish isotropic crystals.
Titanaugite: Exhibits pronounced anomalous interference colors.
Mineralogical Notes:
Hauyne is a sodium-rich, sulfate-bearing feldspathoid mineral in the sodalite group. It is a key indicator of silica-undersaturated magmatic systems and typically occurs in phonolite, nephelinite, tephrite, and hauyne-bearing basanite.
Note on Anomalous Interference Colors:
Titanaugite in this sample contains elevated titanium (3.7 wt.% TiO₂), contributing to strong pleochroic absorption. This absorption affects the transmission of light through the crystal, leading to deviations from standard interference colors based on birefringence alone. The resulting effect known as anomalous interference coloration is primarily caused by high titanium and iron content.
Provenance and Special Note:
This sample was collected from Tahiti by the late Dr. Francie H. Brown (University of Utah). Two thin sections were prepared: one remains in the BH250 collection, and the other is housed at the University of Utah. According to Dr. Brown, the original outcrop is no longer accessible due to the construction of an airport tarmac.
Students in mineralogy courses at Carleton have consistently admired this thin section especially for its striking hauyne. Please handle this irreplaceable sample with great care.
Optical Properties: Hauyne: Beautiful, fuzzy, bluish isotropic crystals.
Titanaugite: Exhibits pronounced anomalous interference colors.
Mineralogical Notes:
Hauyne is a sodium-rich, sulfate-bearing feldspathoid mineral in the sodalite group. It is a key indicator of silica-undersaturated magmatic systems and typically occurs in phonolite, nephelinite, tephrite, and hauyne-bearing basanite.
Note on Anomalous Interference Colors:
Titanaugite in this sample contains elevated titanium (3.7 wt.% TiO₂), contributing to strong pleochroic absorption. This absorption affects the transmission of light through the crystal, leading to deviations from standard interference colors based on birefringence alone. The resulting effect known as anomalous interference coloration is primarily caused by high titanium and iron content.
Provenance and Special Note:
This sample was collected from Tahiti by the late Dr. Francie H. Brown (University of Utah). Two thin sections were prepared: one remains in the BH250 collection, and the other is housed at the University of Utah. According to Dr. Brown, the original outcrop is no longer accessible due to the construction of an airport tarmac.
Students in mineralogy courses at Carleton have consistently admired this thin section especially for its striking hauyne. Please handle this irreplaceable sample with great care.
Coverage
Location: Tahiti
Creator
Bereket Haileab
Source
From the rock collection of Bereket Haileab. Sample BH250-60b. Housed at Carleton College in Minnesota.
Contributor
Frank Brown
Type
Thin section
Relation
Collection
Citation
Bereket Haileab, “BH250-60b,” BH250 Mineralogy Teaching Collection, accessed April 25, 2026, https://bereket-haileab.geology.sites.carleton.edu/items/show/70.