BH250-56

Title

BH250-56

Subject

Granitic pegmatite (Biotite and hornblende)

Description

Major Minerals: hornblende, biotite, plagioclase
Minor Minerals: calcite (secondary), very large sphene (titanite), tiny isotropic mineral
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BH250-56 exhibits a pegmatitic texture with large hornblende and biotite crystals. It is a coarse-grained igneous rock, typically granitic in composition, formed from late-stage crystallization of magma.

Mineralogy:

  • Biotite and hornblende: Common in granitic pegmatites, especially in hydrous compositions; large crystals are typical.

  • Sphene (titanite): Large crystals present.

  • Plagioclase feldspar: Anhedral crystals observed.

  • Calcite: Likely formed from late-stage hydrothermal activity or interaction with carbonate wall rocks, rather than primary igneous crystallization.

Creator

Bereket Haileab

Source

From the rock collection of Bereket Haileab. Sample BH250-56. Housed at Carleton College in Minnesota.

Type

Thin section and hand sample

Relation


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Collection

Metamorphic Rocks

Citation

Bereket Haileab, “BH250-56,” BH250 Mineralogy Teaching Collection, accessed April 25, 2026, https://bereket-haileab.geology.sites.carleton.edu/items/show/65.

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