Crystal Structure
Triclinic plagioclase end-member.
Elemental Composition (by mass)
| Element | Mass % | Visual |
|---|---|---|
| O Oxygen | 48.81% | |
| Si Silicon | 32.13% | |
| Al Aluminum | 10.29% | |
| Na Sodium | 8.77% |
Computed from simplified end-member formula. Solid-solution series, water content, and trace substitutions cause real-world variation.
IMA Abbreviation (Whitney-Evans 2010)
Ab
→ Albite
Na-plagioclase
Standard symbol from American Mineralogist (Whitney & Evans, 2010). Used in thin-section labeling, phase diagrams, and IMA-style species records.
Pronunciation
/ˈælbaɪt/
↔ AL-bite
Latin albus (white)
Luster
vitreous→pearly
Pearly on basal cleavages.
Diaphaneity (Transparency)
translucent
Plagioclase end-member.
Specific Gravity
2.60–2.65
g/cm³
light
Na-plagioclase end member.
For comparison: water = 1.00, glass ≈ 2.5, quartz = 2.65, corundum ≈ 4.00, galena ≈ 7.50, gold ≈ 19.3.
Twinning Laws
Albite lawlamellar
Repeated polysynthetic twins on {010}. Fine striations on basal pinacoid visible to the eye.
Pericline lawlamellar
Parallel to b-axis; visible as additional striation set.
Cleavage & Fracture
Cleavage:
good 2 directions ~86° {001}/{010}
Fracture:
uneven
Plagioclase end-member; striations visible on {001}.
Market availability: Common
Widely available in most dealer stocks. Specimens span all price tiers.
PolymorphsShares the formula
NaAlSi3O8 with: Monalbite — same chemistry, different crystal structure.Mohs 6–6.5
Vickers (~) 820 HV
Knoop (~) 870 HK
Nickel–Strunz
9.FA.35Dana
76.01.03.05Geological setting
Plutonic igneousPegmatite
Element composition by mass
Formula: NaAlSi₃O₈ · molar mass: 262.22 g/mol
| O | 48.81% | |
| Si | 32.13% | |
| Al | 10.29% | |
| Na | 8.77% |
Computed from atomic weights (IUPAC 2021). Site-occupancy groups (Fe,Mn) split equally.
GroupFeldspar Group
Mohs Hardness
6–6.5
Albite sits at 6–6.5 on the Mohs scale — just hard enough to scratch glass.
Colors:
Streak
White
White
Crystal system
Triclinic
Triclinic
SilicatesSilicates (Tectosilicates — Feldspars)
TL;DR · 1 min read
Albite (NaAlSi₃O₈) is the sodium end-member of the plagioclase feldspar series and forms a complete solid-solution series with anorthite (Ca-endmember). Cleavelandite is the platy collector variety from pegmatite pockets — often paired with tourmaline, beryl, and lepidolite.
Albite (NaAlSi₃O₈) is the sodium end-member of the plagioclase feldspar series and forms a complete solid-solution series with anorthite (Ca-endmember). Cleavelandite is the platy collector variety from pegmatite pockets — often paired with tourmaline, beryl, and lepidolite. Major rock-forming mineral in granites and pegmatites.