Guide
Neptunite specimens for sale
18 for sale · $120–$5,000 USD
128 in the gallery
Neptunite is a silicate mineral that typically forms dark, contrasting crystals with a glassy to resinous luster. It commonly occurs in prismatic to tabular habit, often intergrown with other minerals such as natrolite or johannsenite, and can display a deep greenish‑black to reddish‑brown color depending on impurities and intergrowths. Clear to translucent crystals are prized when they survive in robust, well‑formed aggregates from alkaline igneous environments.
- Formula
- KNa2Li(Fe2+)2Ti2[Si4O12]2
- Rarity
- Rare
- Stability
- Stable
- Collector interest
- Moderate Interest
- Classification notes
- Silicate, cyclosilicate; neptunite group
Key characteristics
- Crystal system
- monoclinic
- Mohs hardness
- 5–6
- Specific gravity
- 3.19–3.23
- Luster
- vitreous
- Transparency
- transparent, translucent, opaque
- Color
- black, brown, red
- Streak
- brown
- Cleavage
- perfect
- Fracture
- conchoidal, uneven
- Crystal habit
- prismatic, tabular, granular, massive
- Gem mineral
- Classic / historic
Buy Neptunite specimens
View all 18Where Neptunite is found
Top localities
- Benitoite Gem Mine45 specimens
- California State Gem Mine13 specimens
- Dallas Mine5 specimens
- San Benito County4 specimens
- New Idria Mining District2 specimens
- California1 specimen
- The Mine1 specimen
Guides
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About Neptunite
Notable specimens have come from classic alkaline complexes and nepheline syenites in North America, including prolific finds in the United States and Canada, where Neptunite is frequently associated with other distinctive minerals. Distinctive aggregates are often found in veins and cavities within peralkaline rocks, and bright, lustrous crystals can occur as isolated prisms or clusters that catch light from multiple angles.
Collectors value Neptunite for its striking contrast against associated minerals and its rarity in well‑formed crystals. The mineral’s unusual chemistry and association with other distinctive silicate minerals add to its appeal, rewarding careful preparation and detailed study of crystal forms and color zoning found in high‑quality specimens.
