Alshedite

Alshedite is an obsolete or varietal name historically used for yttrian titanite (a yttrium-bearing variety of titanite, also called keilhauite). It is not recognized today as a distinct mineral species by the International Mineralogical Association (IMA), but it appears in older mineralogical literature and collector references.

🌍 Origins and Naming

• Name Origin: The name “Alshedite” (sometimes spelled Alshedit) was applied to titanite specimens enriched in yttrium.
• Type Locality: Kragerø, Telemark, Norway — a classic site for rare titanite varieties.
• Status: Considered a synonym or varietal name; modern classification treats it as yttrian titanite (keilhauite) rather than a separate species.

🔬 Chemical and Structural Properties

• Base Formula (Titanite): CaTiSiO₅
• Alshedite Composition: Titanite with partial substitution of Ca²⁺ by Y³⁺ and other rare earth elements.
• Crystal System: Monoclinic.
• Color: Brownish, reddish-brown, or dark hues (due to Y and REE substitution).
• Habit: Typically small prismatic crystals, often granular.
• Hardness: ~5–5.5 on Mohs scale.
• Specific Gravity: ~3.5–3.6 (slightly higher than pure titanite due to Y content).
• Luster: Adamantine to resinous.

⚙️ Geological Occurrence

• Found in alkaline igneous rocks and metamorphic deposits rich in rare earth elements.
• Localities:
  • Kragerø, Telemark, Norway (classic occurrence).
  • Arendal, Aust-Agder, Norway.
  • Other Scandinavian pegmatites and REE-bearing rocks.
• Associated Minerals: Zircon, allanite, monazite, and other REE-bearing silicates.

📖 Scientific and Collector Significance

• Petrology: Illustrates how titanite incorporates rare earth elements like yttrium.
• Collectors: Rare and usually small crystals; valued for locality and historical naming rather than aesthetics.
• Modern Status: Today, specimens labeled “Alshedite” are classified as yttrian titanite (keilhauite).

✨ Conclusion

Alshedite is an obsolete name for yttrian titanite (keilhauite), a rare Y-bearing variety of titanite. It was first described from Norway and remains of historical interest, but modern mineralogy treats it as a titanite variety rather than a distinct species.

In short: Alshedite = old name for yttrian titanite (keilhauite), rare REE-bearing titanite variety, first found in Norway.