Staurolite Value, Price, and Jewelry Information
Staurolite crystals in opaque cross shapes are popular gemstones. However, this material is very rarely transparent or facetable. These dark colored gems would make very durable jewelry pieces.
The International Gem Society (IGS) has a list of businesses offering gemstone appraisal services.
|Crystallography||Monoclinic (pseudo-orthorhombic). Crystals prismatic, typically twinned at 60° or 90°, the latter termed fairy crosses; massive.|
|Colors||Dark brown, reddish brown, yellowish brown, brownish black.|
|Luster||Vitreous to resinous.|
|Birefringence||0.011 - 0.015.|
|Cleavage||Distinct 1 direction.|
|Transparency||Opaque to translucent, transparent (rare)|
|Absorption Spectrum||Not diagnostic. Weak band at 5780, strong at 4490. See "Identifying Characteristics" for zincian staurolite.|
|Formula||(Fe,Mg,Zn)2Al9Si4O23(OH) + Zn or + Co.|
|Pleochroism||Distinct: colorless/yellow or red/ golden yellow.|
|Optics||Optics: a = 1.739-1.747; β = 1.745-1.753; γ = 1.752-1.761. Biaxial (+), 2V = 82—90°. Indices increase with iron content.|
|Etymology||From the Greek stauros and lithos, meaning “stone cross.”|
|Occurrence||Staurolite is a mineral of metamorphic rocks, such as schists and gneiss.|
|Inclusions||Crystals (garnet, quartz), may have surface cavities.|
Staurolites can form as twinned crystals at either 60° or 90°, creating interesting natural cruciform pieces. Thus, these stones are popularly called “fairy crosses” or “fairy stones.” They’ve inspired a number of symbolic associations over time. According to George F. Kunz, the noted mineralogist and folklorist, a Virginia legend holds that the tears of fairies crying at the news of Christ’s death turned into these stones. People from many cultures throughout history have also treated cross-shaped staurolites as good luck charms.
Crystals with both 60° and 90° twinning are extremely rare.
“Staurolite (rough and cut set),” Keivy, Keivy Mountains, Kola Peninsula, Russia. 4.3 x 3.1 x 2.3 cm (crystal), 1.08-ct (brilliant pear-cut gem, source unknown). © Rob Lavinsky, www.iRocks.com. Used with permission. (Gem photo cropped to show detail and slide show created to facilitate comparison).
Though very rare, zinc-bearing staurolites have lighter colors and make more attractive cut gems.
- Specific Gravity: 3.79.
- Refractive Indices: 1.721-1.731.
- Absorption Spectrum: Strong broad bands at 6100 and 6320, weaker narrow bands at 5315; spectrum absorbed beyond 4900.
- Pleochroism: Trichroic, green/red/yellow.
- Color Change: May be red-brown in incandescent light, yellow-green in daylight.
A deep blue, strongly pleochroic cobalt-bearing staurolite from Lusaka, Zambia.
Staurolite crystals aren’t rare. However, people have created simulations of cruciform crystals due to their popular symbolic associations. The manufacture of faux “fairy crosses” goes back at least a century. In the 1910s and 1920s, the mineralogist Joseph K. Roberts examined specimens from Georgia, Tennessee, and Virginia and learned how some were likely created. In a 1934 article in American Mineralogist, Roberts noted that 90° “Roman Cross” shapes dominated the market, despite being the rarer variety. He discovered that many were cut from much softer talcose material and filed into shape. Then, these pieces were soaked in linseed or other oils to darken them. (A GIA note from 1963 describes a similar talcose imitation dipped in paraffin).
Apparently, the demand for transparent, facetable staurolite hasn’t yet generated the same level of industrious deception.
Cruciform staurolites may be filed to improve the appearance of their terminations or smooth out surface cavities. Weathering may create a pitted appearance on natural specimens. However, Roberts also noted that some imitations received artificial pockmarks to appear more natural!
Brazil and Switzerland will occasionally produce facetable crystals.
Other notable crystal sources include
- United States: Connecticut; Georgia (the state mineral); Maine; New Hampshire; New Mexico (fine twinned crystals); North Carolina; Vermont.
- Canada; France; Russia; Scotland; Spain.
- Lusaka, Zambia: lusakite.
Always tiny, cut staurolites from Brazilian or Swiss material generally weigh under 2 carats.
- Smithsonian Institution (Washington, DC): 3.0 (dark brown. Brazil).
With a hardness of 7-7.5, faceted staurolites would make durable jewelry stones. However, stones with cavities associated with fractures that extend to the surface may have structural weakness. These may also collect dirt and grime. (Staurolite surface cavities typically occur when mineral inclusions weather out of the stone). Stay on the safe side and clean any staurolites, faceted or natural crystals, with a soft brush, mild detergent, and warm water. Otherwise, these gems require no special care. Consult our gemstone jewelry cleaning guide for more recommendations.