Rob Lavinsky, iRocks.com – CC-BY-SA-3.0 [CC-BY-SA-3.0], via Wikimedia Commons
Triphylite Value
Values of tryphylite vary considerably, due to their rarity and demand. Some have sold for $250 a carat. At auction, demand has driven prices as high as $4,500 per carat.
The International Gem Society (IGS) has a list of businesses offering gemstone appraisal services.
Triphylite Information
| Data | Value |
| Name | Triphylite |
| Crystallography | Orthorhombic; crystals prismatic, often with rounded faces, but very rare: usually massive, cleavable, and compact. |
| Colors | Greenish gray, bluish gray; alters to brownish or blackish hues (lithiophilite is clove brown, yellowish brown, honey yellow, salmon). |
| Luster | Vitreous; resinous to sub resinous. |
| Hardness | 4-5. |
| Density | 3.42. Pure Fe end of series = 3.58, pure Mn end (lithiophilite) = 3.34. The halfway point (Fe: Mn = 1:1) I 3.52; density is not linear with Fe: Mn ratio. |
| Birefringence | 0.006—0.008. |
| Cleavage | Perfect 1 direction; fracture subconchoidal to uneven. |
| Stone Sizes | Large stones conceivably could be cut from some of the immense crystals found in South Dakota, but these are usually opaque or altered. Tiny brown stones have been cut from Brazilian material. This is the kind of mineral that could surprise the world of gem species collectors by appearing as cuttable crystals from a newly discovered deposit at almost any time. |
| Luminescence | None reported. |
| Spectral | Not diagnostic. |
| Formula | Li(Fe+2, Mn+2)PO4 + Mg. Series to Lithiophilite. |
| Pleochroism | Absent or very weak; some lithiophilite may show deep pink/pale greenish yellow/pale pink. |
Comments by Donald Clark, CSM IMG
The IGS received the extraordinary privilege of examining one of the world’s rarest gems, tryphylite. (Also spelled triphylite.) These gems are from a new discovery in Brazil. This was exciting because it has been fifteen years since the last discovery of facetable material. In addition, the new deposit shows characteristics that were previously unknown.
As sometimes happens, new deposits show different, or a wider range of properties than previously reported. As any long-term student of gemology knows, the reported properties of gems expand over time. Textbooks written in the 1950’s show a narrower range of properties than those written in the 1990’s. The reason is that more gems have been examined and more information is now available.
With a gem as rare as tryphylite, very few specimens have ever been examined. In addition, this mineral is in series with Lithiophilite. That allows new blends to appear that have been previously unobserved.
Previous examples of this gem were just melee sized and have very little pleochroism. Gems from the new discovery run up to two carats in size. They also have beautiful orangish/brown and green coloring, similar to andalusite. A summary of the properties is listed above.
In Greek tryphylite means “family of three” and is probably referring to the three ions: lithium, iron, and manganese. Tryphylite is one of the phosphate minerals. It forms a solid solution series with the mineral lithiophilite. Lithiophilite’s formula is nearly identical to tryphylite, Li(Mn+2,Fe+2)PO4. It differs from tryphylite by being rich in manganese instead of iron. Lithiophilite is slightly less dense, due to its lower iron content. It is pinkish to greenish brown whereas tryphylite’s color is usually a gray shade of blue or green. The new discovery clearly shows the blend, being clove brown and grayish green.
Tryphylite does not usually form in distinct crystals. Most crystals are embedded in other stone and appear as compact masses, or intergrown crystal clumps. Most of the material found is limited to cabochon cutting. Faceting material is very rare.
Triphylite is a primary phosphate mineral. It alters easily into other phosphate minerals, especially manganese phosphates. Some of the secondary phosphate minerals are eosphorite, reddingite, sicklerite, hureaulite, fairfieldite, dickinsonite, stewartite, vivianite, salmonsite, strengite, purpurite, heterosite, phosphoferrite, wolfeite, triploidite and fillowite.
Optics
a =1.689-1.694; β=1.689-1.695; γ= 1.695-1.702.
Biaxial (+)
May sometimes be observed optically (-) and uniaxial interference figures may be observed, depending on the Fe: Mn ratio. Refractive indices increase with Fe content but may be substantially decreased if Mg substitutes for (Fe, Mn).
Occurrence
As a primary mineral in granitic pegmatites, often altered to a wide array of secondary phosphates.
- Black Hills, South Dakota: as enormous crystals up to 6 feet long.
- New Hampshire: excellent crystals at Chandler’s Mill, Palermo, Grafton Center, North Groton.
- Massachusetts; Maine: Pala, California.
- Germany; Finland; Sweden; France; Brazil.
Name
From Greek words meaning threefold and family, in allusion to the presence of three cations.
