FOSSILIFEROUS ROCKS

( Singular nouns:  Fr- fossile-riche roche/roche fossilifere; Ger- fossilienhaltig Gestein;
Nor- fossilførende stein; Rus- ... )

FOSSILIFEROUS ROCKS (See also the AMBER entry.)

A. Iridescent nacreous aragonite outer layers of a fossil ammonite (Placenticeras meeki), from Bearpaw Formation exposures on the Kormos Farm, Magrath, Alberta, Canada.  This material, which exhibits several diverse qualities and color intensities (cf. "B"),  occurs sporadically in the vicinity of Lethbridge, Alberta, Canada.  Pieces incorporated in jewelry have been marketed as ammolite, calcentine and korite. Canadian Museum of Nature. (© photo by Frederick H. Pough)

B. Iridescent aragonite. Pendant (greater dimension - 4.0 cm) of ammolite with fractured outer layer of a fossil ammonite (Placenticeras intercalare) from near Lethbridge, Alberta, Canada. (© courtesy of Korite International Ltd.)

C. Fossil favosites coral carved and polished to resemble a porcupine (height - ca. 10 cm).(photo by D.L. Brittain)

D. Petoskey stone pendant (greater dimension - ca. 5.0 cm). (© photo by Dick Dietrich)

E. Petrified wood, Petrified Forest National Park, Arizona. (© photo by Dick Dietrich)

F. Fossiliferous rock. Well prepared and in part polished slab (height - ca. 100 cm) with diverse Mesozoic cephalopods. Comstock Rock Shop, Virginia City, Nevada. (© photo by Sue Monroe)

G. "Turritella" agate polished piece -- see at end of OTHER NAMES list.

DESCRIPTION: The term fossiliferous rock may be applied to any fossil-bearing rock. Those mentioned herein are only a few examples of many that have been used as gemrocks.  Some fossiliferous rocks have been selected for use as gemrocks because of the identities of their contained fossils; others have been chosen because of the patterns their included fossils give when cut in certain directions. The name usually applied to these rocks in the marketplace is the name of the rock preceded by either the name of the predominant fossil (e.g., coraline marble) or the adjective fossiliferous if the rock contains more than one kind of fossil with none predominant (e.g., fossiliferous limestone).  Several other names, however, have been used, most of them based either on the locality from which the rock came or someone's idea of a term that might increase sales of anything made from the rock. Because each of these gemrocks is so-to-speak unique, descriptions, noteworthy localities, etc. are included in the comments given after several of the materials listed under the OTHER NAMES subheading.

OTHER NAMES:

G."Turritella" agate polished piece (width - 4 cm), Wamsutter Ridge, southwestern Wyoming.  (© photo by courtesy of Webminerals s.a.s., www.webgemshop.com)

USES: Necklaces (dating to ca. 28,000 B.C.) that include fossilized pelecypods and gastropods as beads have been recorded  from a Gravettian Culture site at Pavlov, which is about 25 km west of Jihlava in central Czech Republic (Dubin,1987). More recently, several gemrocks that are best designated as fossiliferous rocks have been used as the "rough" for fashioning gemstones -- usually for larger pieces such as brooches, pendants, belt buckles and ornament bars for bolo ties;  many of these rocks have also been used as the rough material from which both functional (e.g., buttons, dishes, bowls and guitar picks) and diverse decorative ornaments (e.g., carved figurines for "whatnots") have been fashioned.  Another group of objects that falls into this category of uses comprises the decorative rocks created by the ultra-fine preparation of fossil-bearing specimens that contain either individual or groups of fossils; several such specimens are displayed in offices and homes because of their so-to-speak artistic appearance and/or value as conversational pieces rather than because of their scientific (i.e., paleontological) value --  see Figure F and examples shown in Jones (1999).  Also, dinosaur bones have been fashioned into such things as pendants, ear rings and cuff links.   In addition, individual fossils -- e.g., well defined trilobites and brachiopods carefully removed from their host rocks -- have been used as pendants by merely drilling holes in or through them for insertion of a post, loop or chain, and some of these kinds of individual fossils have been used to make molds for, for example, gold castings that are used as pendants, earrings,  tietacks, etc.

Attention is also directed to the statement  about the clams that are replaced at least in part by carnelian -- see Chalcedony entry, under  the USES subheading.

                                                                                                  
H. Ammonite pendant.  This cephalopod (41 cm. - height as shown) is from
Madagascar.   It was sliced to show the internal structure of its shell before being mounted for use as a pendant.  The reverse (out) side exhibits a multicolored sheen similar to that exhibited by mother-of-pearl. The necklace to which it is attached is faceted tigers-eye.  (© photo by courtesy Gail Coppock,  http://www.gailsart.com/Jewelry.html) 

OCCURRENCES: Most fossils occur in sedimentary rocks; a few occur in volcanic rocks;  fewer occur in the metamorphosed products of these rocks;  [and] some petrified plants and animals have been found in unconsolidated sediments.

LOCALITIES: Widespread -- a few examples are noted in the statements following the terms listed under the OTHER NAMES subheading.

REMARKS: I have always been somewhat nonplussed about the origin -- or perhaps more, the general application -- of the term fossil:  It comes from the Latin fossilis(dug up), and my observations and experience indicate that fossils are less frequently dug up than minerals and rocks, and especially ores.  To add to my bewilderment, I early learned that Georgius Agricola (Georg Bauer, 1494-1555) is widely recognized as the "Father of Mineralogy" because of his classic De Natura Fossilium, which is widely considered to be the first textbook of mineralogy.  In any case, since at least the middle 1600s, the term fossil has been applied almost exclusively to remains of plants and animals, most of which have been so-to-speak lithified.

The Petoskey stone and the city in Emmet County,  in the northwestern part of Michigan's lower peninsula, were named after Chief Ignatius Petoskey (1787-1885) who founded the community.  Petoskey's father was a French fur trader and his mother was an Odawa (Ottawa) Indian.  His first name Ignatius was bestowed upon him by Jesuit missionaries;  his Odaw name was, as spelled by the Indians -- in order make it closer to their ponounciation -- was  Biidassige or Pe-to-se-ga, which translated means "One who brings light" or "Light shines through."  In any case, his name became recorded as Ignatius Petoskey.  One has to wonder if  "Biidassige stone"  or even "Petosega stone" would have gained the wide recognition that Petoskey stone has. 

Ammolite (etc.), much of which occurs in relatively thin pieces, is commonly impregnated with a polymer to give them strength and, in some cases, increase the depth of their diverse colors -- see Figure B.

The name buffalo stone was given by North American Plains Indians to fossils considered to be charms that would insure those who carried them success while hunting buffalos.

Petrified wood is Arizona's representative among the nearly 200 commemorative "stones," including at least one from each of the 50 states, that are mounted inside the Washington Monument.

The Petoskey stone is the official state stone of Michigan.  Petrified wood is the state fossil of Arizona, the state stone of Mississippi, and the state gem of Washington.  Teredo petrified wood is the state fossil of North Dakota.  Petrified palmwood is the state stone of Texas.  The "sea scorpion," the euripterid Eurypterus remipes, is the state fossil of New York.

SIMULANTS: As indicated by a story frequently repeated within the geological community -- although apparently not wholly correct (Sanders, 1960) -- fakery of fossils is nothing new:   Briefly, that story holds that several of the "fossils" described and figured by Johann Bartholomaeus Adam Beringer -- Professor of Natural History, University of Wurzburg -- in his treatise "Lithographiae Wirceburgensis" (1726) were carved by students, who placed them where he would find them, which he did, only later to learn he had been so-to-speak become the spokesman for a hoax.  Another such hoax that involves the "Cardiff Giant," first reported as a fossil man, is described in the third paragraph under the REMARKS subheading in the ALABASTER entry.

Assembled ammolite - strictly speaking, these units are not silimulants.  They are triplets -- e.g., a  "Triplet, consisting of a glass top and mosaic inlay of natural fossilized ammonite shell fragments with a thick black backing,"  (Johnson et al., 2000, p.261-262).  - [Many assembled stones can be seen to be such by examination with a handlens;  also, the glass of this one has a superior hardness (H. ~5).].

***Glass - a glass bead apparently made to resemble fossiliferous limestone is illustrated by Liu (1995, p.222). - [appearance].

***Plastic (in part) -The following are hybrids rather than simulants per se. -- Whereas most cabochon ammolite doublets and triplets have a thin slice of ammolite along with one or two plastic layer(s), in some of the more recently marketed ones, the ammolite layer consists of a plastic-bound mosaic of small fragments of ammolite (Johnson et al., 2000).

***Resin - Two examples: 1.Winterthur has recently advertized and illustrated 12-inch spheres ("faux seashell sculpture[s]") the surfaces of which are covered with mollusc-shaped masses in relief.  2.Design Toscano has recently advertized some cast resin faux fossil display pieces as follows: "Recently the remains of two fossilized creatures thought to be Dragons, arrived at our offices via a mysterious Parcel Post. . . We opened the . . . wooden crates, and unfolded the burlap . . . to discover bas-relief, two-toned . . . dragon fossils unearthed in Wales and sent by Dr. Rex Solomon, an eccentric British anthropologist. . . . [you can be the owner of and thrilled by] the 'authenticity' of these [fossils]."  - [Appearance suffices for any of these I have seen; if one is undecided, check with a paleontologist.].

Snake skin agate - misnomer applied to some chalcedony within lava (?) that roughly resembles snake skin -- e.g., those from Grants area, Cibola County, New Mexico. - [Appearance suffices.].

***Two additional examples of so-to-speak falsifying fossils are noted in the AMBER entry, under the SIMULANTS subheading.

Also, see "fossil turtles" under the REMARKS subheading in the SEPTARIUM entry.

REFERENCES: No general reference.  BUT a number of paleontology and historical geology textbooks contain indirectly interesting information about fossils and their occurrences; examples are Black, 1988 - paleontology;  and Wicander and Monroe, 1993 - stratigraphy.

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Last update: 8 July  2013
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