Danburite Mineral Overview

Mineral name: Danburite
Mineral class: Silicate (sorosilicate)

Known Facts

• Chemical formula: CaB₂Si₂O₈
• Crystal system: Orthorhombic
• Mohs hardness: 7–7.5
• Color range: Colorless, white, pale yellow, light pink, brown
• Luster: Vitreous
• Streak: White
• Cleavage: Distinct to perfect in one direction
• Fracture: Conchoidal to uneven
• Specific gravity: Approximately 2.9–3.0
• Common locations: Mexico, Japan, Myanmar, Russia, United States
• Uses: Gemstones, collector specimens
• Similar minerals: Topaz, quartz, phenakite

Physical and Optical Characteristics

Danburite typically forms:

• Elongated prismatic crystals
• Crystals with well-defined terminations
• Sometimes massive or granular aggregates

Crystals are often transparent to translucent, and high-quality specimens can be quite clear.

Color is usually colorless or very pale, though light yellow, pink, or brown tones may occur due to trace impurities.

The luster is vitreous, giving the mineral a glassy appearance. With a hardness of 7 to 7.5, Danburite is relatively durable.

A notable feature is its good cleavage, which can influence how it breaks and how it is cut for gemstones.

Chemical Composition and Structure

Danburite has the formula:

• CaB₂Si₂O₈

It is a calcium boron silicate, containing:

• Calcium (Ca)
• Boron (B)
• Silicon (Si) in silicate groups

Structurally, Danburite is classified as a sorosilicate, though its structure is somewhat intermediate and can resemble framework arrangements in some respects.

Boron plays an important role in the structure, contributing to:

• Crystal stability
• Distinct physical properties compared to more common silicates

Formation and Geological Occurrence

Danburite forms in contact metamorphic and hydrothermal environments, particularly in boron-rich systems.

Typical formation settings include:

• Skarns (metasomatic zones between igneous intrusions and carbonate rocks)
• Hydrothermal veins
• Metamorphosed limestones

It forms under conditions where:

• Boron-rich fluids interact with calcium-bearing rocks

Common associated minerals include:

• Calcite
• Quartz
• Fluorite
• Other boron-bearing minerals

Common Locations

Notable occurrences of Danburite include:

• Mexico: Charcas, San Luis Potosí (famous for gem-quality crystals)
• Japan: Classic locality (Danba region, source of the name)
• Myanmar: Gem-quality material
• Russia: Various deposits
• United States: Connecticut (type locality, Danbury)

Mexico is particularly known for large, clear crystals.

Uses and Practical Significance

Danburite is valued primarily for:

Gemstones

• Cut into faceted gems, often resembling topaz
• Appreciated for:
  • Clarity
  • Durability
  • Subtle coloration

Collecting

• Well-formed crystals are highly desirable

It has no major industrial applications.

Similar and Related Minerals

Danburite may be confused with:

• Topaz: Similar clarity and hardness but different composition and cleavage
• Quartz: Slightly softer and lacks cleavage
• Phenakite: Similar appearance but different chemistry

Distinguishing features include:

• Boron content
• Crystal habit
• Cleavage characteristics

Identification Notes for Collectors

• Look for clear, prismatic crystals in skarn or hydrothermal environments
• Check for good cleavage and high hardness (7–7.5)
• Note association with calcite and fluorite
• Compare with topaz and quartz for hardness and cleavage differences
• Use gemological or laboratory testing for confirmation

Danburite is a boron-bearing silicate mineral, recognized for its clarity, prismatic crystals, and occurrence in boron-rich metamorphic environments, and is valued both as a gemstone and a collector mineral.