(Fr- serpentin; Ger- Serpentin; Nor- serpenti; Rus- )
SERPENTINE, group name with general formula: (Mg,Al,Fe,Mn,Ni,Zn)2-3(Si,Al,Fe)2O5(OH)4.
A. Serpentine flower (dyed) and leaf arrangement (height - 15 cm) within a serpentine bowl from an unknown locality. F.S. Dietrich collection. (© photo by Dick Dietrich)
B. Serpentine elephant (greatest height - ca. 14.5 cm), from Zimbabwe (formerly Southern Rhodesia). Carved by artisans of the Shona Tribe of Zimbabwe. Unconventional Lapidarist. (© photo by Cindy Fowler, www.unconventionallapidarist.com)
C. Williamsite beads (length of strand - 45 cm), bracelet and earrings. F.S. Dietrich collection. (© photo by D.R. Fisher)
D. Serpentine. Clock mounting (height - 14 cm) from unknown locality. R.V. Dietrich collection. (© photo by D.R. Fisher)
E. Serpentine. Zimbabwe (formerly Rhodesia) carving (height - 9.5 cm). R.V. Dietrich collection. (© photo by Dick Dietrich)
DESCRIPTION: Several diverse predominantly
serpentine materials are used as gemrocks. The diversity
notwithstanding, most gemrock serpentine can be
characterized as massive, translucent to subtranslucent, and either
relatively uniform green, greenish yellow or yellowish green or
multicolored. The following are the rather rather wide
Colors - diverse shades of red, green, yellowish, bluish, brown, nearly black, and rarely white, with some pieces virtually one color whereas others are bi- or multicolored and best characterized by such terms as blotched, mottled, spotted, streaked, or even banded
H. typically 2½ -4, but up to 5½ for some varieties, such as bowenite
S.G. 2.2 - 2.9
Light transmission - translucent to opaque
Luster - dull to waxy
Miscellany - often recorded as having a "greasy feel." Many serpentine-rich rocks used as gemrocks contain macroscopically discernable grains of one or more other minerals such as calcite, magnesite, dolomite, talc, chromite, and magnetite.
OTHER NAMES: Serpentine means different things to different people, and its application has changed with time in both mineralogical and petrological publications:
In mineralogy, serpentine, once a widely accepted mineral name, is now accepted only as a codesignator of the Kaolinite-Serpentine group: This group includes 20 minerals, several of which have long been considered to be so-to-speak subspecies of serpentine -- e.g., antigorite; clino-, orth- and para-chrysotile (each usually spelled without the hyphen); and lizardite (see Mandarino, 1999). In addition, materials formerly given names such as bowenite and williamsite have been shown to be varieties of recognized species -- e.g., these two are varieties of antigorite -- so these names are not recognized by professional mineralogists.
In petrology, until about the middle of the 20th century, rocks composed largely of one or more of the serpentine minerals were usually also called serpentine. Then, in order to distinguish between the mineral(s) and the rock, some petrologists thought it only prudent to call the rocks serpentinite. Unfortunately, this change in nomenclature -- perhaps because it was neither loudly nor widely expounded -- has not been embraced by many geologists. Therefore, masses that consist largely of serpentine minerals have been referred to in both older and recently published geological reports by names such as the Staten Island Serpentine (of Staten Island, New York and adjacent New Jersey) as well as by names such as the Cedar Hill Serpentinite (of Maryland, Pennsylvania and Delaware).
In the marketplace, the terminology has been more consistent over the years: The term serpentine has been and continues to be applied almost exclusively.. In addition, however, names of species, varieties, and trade names have been given to several serpentine-rich gemrocks. More than 30 names were listed by the early 1960s -- 29 by Faust and Fahey (1962) and three additional ones by Johannsen (1928). Several of these names have been shown to have been applied to non-serpentine minerals, to mixtures or to indicate only slight differences in color and/or texture. A few fairly frequently used names for gemrock serpentine follow:
USES: Jewelry and diversely fashioned masses such as plaques, vessels, bases and frames for clocks, pen and ink desk sets, etc.; and even for chop sticks. In addition, serpentine has been used widely as a jade substitute and a dyed antigorite has been recorded as having been marketed as chalcedony (see CHALCEDONY entry).
OCCURRENCES: Origins of most serpentinites are not well agreed upon by geologists; there is, however, fair agreement that at least some serpentinite masses represent altered olivine-rich igneous rocks.
NOTEWORTHY LOCALITIES: France; Norway; as sporadic, relatively large masses in the California Coast Ranges; near Grafton, Windham County, Vermont; a number of localities on islands in and near Baffin Bay have yielded serpentinite used by Inuit carvers, and other deposits are actively sought in Nunavut Territory, Canada (see Wight, 2013O; several additional localities have been so-utilized -- a few of them are given following the appropriate names under the OTHER NAMES subheading.REMARKS: Serpentine is an adjective that means serpent-like -- i.e., snake-like -- as well as a mineral name. It seems ironic to some people -- but quite appropriate to others -- that it has long been thought that people who carry anything made from the mineral serpentine have protection from snake bites. Indeed, some people believe this association led to giving the mineral its name; others, however, think it more likely that the mineral was so-named (apparently first recorded by Agricola, 1546) because the colors and patterns of some of the fairly common dark green mottled serpentinites resemble the skins of some snakes. Whichever, the following lines from a poem attributed to Orpheus and said to have been written in the 4th century A.D., are interesting; as given, they are from King (1865, p.384).
"No more the trailing serpent's tooth to fear.
Let him who by the dragon's fang hath bled,
On the dire wound Serpentine powdered spread,
And in the stone his sure reliance place,
For wounds inflicted by the reptile race."
Several adjectives have been applied to diverse
serpentines, especially those used as gemrocks; Noble, precious,
and common are examples. I consider nearly all of them quite
subjective, if not ambiguous, and suggest that whenever anyone
encounters or is confronted with such terminology, (s)he should try to
get the marketer, or whomever, to supply a more definitive name or
Serpentine is sometimes dyed and/or otherwise treated.
Serpentine not otherwise identified is the official state rock of California, and in 2010 this designation has been a subject of widespread discussion because a state legislator has suggested that it should have this designation dropped because of its association with asbestos. Bowenite from its type locality in Rhode Island has been referred to as Rhode Island jade and, in 1966, was decreed the official state mineral of Rhode Island. In 1967, a bowenite cabochon cut and polished by Mrs. John C. Rogers of Warwick, Rhode Island became part of the "Our Mineral Heritage Brooch," presented to then First Lady Mrs. Lyndon Johnson by the American Federation of Mineralogical Societies. This brooch is now in the collections of the Smithsonian Institution.
Miskeyite - "Compact chlorite (pseudophite)
used as an ornamental stone from St. Gallenkirch, Vorarlberg, Austria"
(Mitchell, 1985); I have been told that this rock closely
jade". Actually several compact, massive green-colored chlorite
rocks resemble serpentine and could serve as serpentine simulants.
- [may require non-macroscopic means].
Nephrite - Although this seems incredulous,
considering the values placed on these two materials, it warrants
mentioning that Wentzell (2004) records and describes a carving as
"Nephrite that Mimics Serpentine." - [Despite the superior
hardness of nephrite, which should suffice to distinguish nephrite from
serpentine, apparently the
fact that this material was coated led to Wentzell's belief that it was
necessary to submit the material to several laboratory tests in order
to establish the material's true identity.].
***Serpentine ware - a Wedgwood china made to resemble serpentine, including verde antique - [Appearance should suffice.].
REFERENCES: No general up-to-date reference; see, however, Faust and Fahey, 1962 and McKague, 1968.
| Top | Home |
R. V. Dietrich © 2013
Revised 11 May 2013
web page created by Emmett Mason