Alabaster
Alabaster is a fine-grained, massive variety of gypsum (calcium sulfate dihydrate, CaSO4·2H2O), prized since antiquity for carving because of its softness and ability to take a smooth polish. Unlike crystalline selenite, alabaster shows no visible crystal faces, appearing instead as a compact, sugary or waxy mass. Its low hardness and solubility in water set it apart from harder ornamental stones like marble, which it is often confused with by name alone.
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Alabaster properties at a glance
| Type | Minerals |
|---|---|
| Chemical formula | CaSO4·2H2O |
| Mohs hardness | 1.5–2 |
| Crystal system | Monoclinic |
| Luster | Vitreous (crystalline); waxy to dull (massive) |
| Streak | White |
| Cleavage | Perfect on {010} (rarely visible in massive alabaster) |
| Fracture | Conchoidal to splintery |
| Specific gravity | 2.3 |
| Transparency | Translucent to opaque |
| Common colors | White, Cream, Pale pink, Yellowish, Gray, Banded |
| Rarity | common |
Geology & background
Alabaster forms where gypsum precipitates from evaporating seawater or saline lake water, typically within thick evaporite sequences interbedded with limestone, shale, and anhydrite. Classic deposits occur in Italy's Volterra region, Egypt's Nile valley quarries used by ancient sculptors, England's Nottinghamshire, and the extensive gypsum beds of the American Southwest and Great Plains. Because gypsum readily recrystallizes and dissolves, alabaster bodies are often riddled with veining, color banding, and small cavities that give each block a unique pattern.
Collectors should keep alabaster dry and away from acidic cleaners, since water can dull its polish and dissolve fine surface detail over time. Because the mineral scratches with a fingernail, carved pieces are vulnerable to abrasion and are best displayed rather than handled roughly. Rockhounds hunting alabaster in the field usually find it as massive nodules or bedded layers rather than terminated crystals, and its soft, faintly translucent character under a light source is the surest field clue.
How to identify Alabaster
Alabaster is soft enough to scratch with a fingernail, a trait that immediately separates it from marble, which resists a fingernail and needs a steel blade to mark it. It typically appears white, cream, pink, or gray with wavy veining, has a white streak, and shows a vitreous to slightly waxy, sometimes translucent luster on cut surfaces. Fracture is uneven to splintery rather than showing a clean cleavage plane in massive form. It is commonly mistaken for marble or soapstone until the fingernail test is applied.
- Compare the specimen's color, luster, crystal habit, grain size, streak, and locality before confirming.
- Use multiple photos when possible, including a fresh surface and a close view of texture.
Where Alabaster is found
Reported from multiple localities worldwide; verify locality against specimen provenance when available.
How much is Alabaster worth?
| Entry-level specimen | $2 |
|---|---|
| Typical collector specimen | $20 |
| Premium specimen | $150+ |
Value depends on size, crystal quality, color, locality, rarity, damage, and provenance.
Common uses
- Collector specimens
- Education
- Field identification
- Industrial or lapidary use when suitable
Interesting facts
- Ancient Egyptian canopic jars and funerary vessels were frequently carved from alabaster because its slight translucency was thought to evoke the glow of skin.
- The word alabaster traces back to an ancient Egyptian town, Alabastron, once famous for quarrying the stone used in perfume jars.
- Because gypsum dissolves slowly in rainwater, outdoor alabaster carvings weather and lose detail far faster than marble statues exposed to the same climate.
Care & safety
Handle as a collector specimen until hardness, cleavage, and fracture are verified.
Avoid inhaling dust. Do not cut, grind, or polish unknown specimens without eye protection and a proper respirator.
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