AVAILABLE CABOCHONS
(Last updated 1/9/09)
On this page I've illustrated just
a few of the many types of cabochons - numbering well over 600
- that I have available for wire-wrapping. (Unfortunately most
of these pix were taken in artificial light, which caused visible
reflections, but I did compensate for spectral differences so
colors are still reasonably true.)
Many different materials that show
interesting colors and patterns can be found in cabs of standard
sizes and shapes at very reasonable prices, including many different
types of agates and jaspers (see under Quartz in Gems-2).
An assortment of such stones is shown below, including flower
jasper (top center left), sodalite (top center; a mineral in its
own right), chrysanthemum stone (top center right; another non-quartz
stone), dalmatian jasper (top right), red jasper (bottom left),
mountain "jade" (bottom center left; actually a jasper),
tree agate (bottom center), and a few less common ones as well,
including Amazon Valley jasper (bottom center right) and ocean
jasper (bottom right). [Note the wide border on the pic below;
just click on the pic to see an enlargement.}
Sometimes it is cutting that adds
to the value of a material, as in the stones shown in the pix
below. I was fortunate enough to stumble into the booth of master
cutter Raul Rojas of Oro Grande, New Mexico at an open air gem
show in Buena Vista, Colorado and came away with these highly
polished yet incredibly thin (2.5 to 3.5mm) matching (and sometimes
mirror image) cabochon pairs that should make spectacular dangle
earrings. As you can see, Mr. Rojas used many different types
of stones and cut them into many interesting shapes, in addition
to selecting materials with marvelous, eye catching patterns.
On the other hand, there are some
jaspers and especially agates that are truly exceptional. One
is Crazy Lace, which derives its name from the fine opaque to
translucent bands that swirl together to create complex and extremely
varied patterns. Much of the material found on the market today
has banding that tends to be various shades of white or gray with
creamy browns, blacks, golds, and occasional pinks or reds, but
material from older collections displays a much wider variety
of bright colors. Crazy lace comes primarily from Chihuahua and
other locations in northern Mexico; the Sierra Santa Lucia mountain
range just west of the village of Benito Juarez is particularly
famous for its production of "Mexican Crazy Lace."
Another special agate is Laguna,
which comes from an area in Chihuahua, Mexico just east of Estacion
Ojo Laguna (Eye Lake), a tiny train stop about 150 miles almost
due south of El Paso, Texas; it is produced by about a dozen claims
running roughly north to south down a 4 mile stretch of the low
mountains located there. Laguna is a nodular "fortification"
type agate known for its tight banding and bright colors, and
is considered to be the most beautiful banded agate in the world.
The bands may be clear, white, or any other color; and
some specimens show over 100 individual bands per square inch.
Striking (and sometimes jarring) color combinations in the banding,
as well as subtle color shifts, are common. Fine specimens can
be very expensive, but I got these slices, well-polished and with
rounded edges - and with what I think are pleasing colors - at
a very reasonable price.
A "new" stone called Polish
Flint - grey to brownish grey in color and showing alternating
dark and light bands (often translucent) in striking patterns
- has recently become popular for use in jewelry, particularly
in Europe. A true flint - a hard cryptocrystalline form of quartz
categorized as a chert that occurs primarily as nodules in sedimentary
rocks such as limestone, it was used extensively for knapping
throughout prehistory. It comes from an area on the northern fringes
of the Swietokrzyskie (Holy Cross) Mountains in central Poland,
between the towns of Ilza and Ozarów, and many ancient
extraction sites and primitive mines are known, the largest and
most famous of the latter being Krzemionki, used by peoples of
many different cultures from ca 3900 to 1600 BC. The oldest finds
of this flint date to the Middle Paleolithic, but its widest distribution
occurred during the Late Neolithic when the Globular Amphora Culture
exported the material, mainly in the form of flint axes; its use
continued regionally well into the Bronze Age. In modern times
it was regarded mostly as a contaminant during the extraction
and making of lime from the limestone that contained it.
In addition to various types of
quartz, interesting and beautiful cabochons can be cut from many
other materials, especially if they have a high silica (ie, quartz)
content. For example, rhyolite is an igneous (ie, volcanic) rock
that typically contains over seventy percent silica; one of the
most attractive is Apache Sage from New Mexico, also called Mimbres
Valley Picture Stone (left; also shown in the bottom earring stone
pic above). Further, if a rhyolite lava is cooled too quickly
to crystallize, it instead forms obsidian; one of the most common
is snowflake (left; due to inclusions of small, white, radially
clustered crystals of cristobalite; also called flower), with
mahogany (center) and rainbow (right; cut so its color bands follow
the shape of a heart) lesser known examples
Nundoorite (top), from an area near
Nundle, Australia, is also mostly quartz, but contains the minerals
andalusite and epidote (the green spots) as well. A stone with
a similar composition is unakite (bottom; named after the Unakas
mountains of North Carolina, where it was first found), another
of my favorites; an altered granite, it is mostly quartz, but
also contains pink orthoclase feldspar and green epidote.
The stones pictured below are a
type of fossiliferous silicified sedimentary rock called mookaite,
named after the principal locality where the rock is dug, namely
an outcrop along Mooka Creek on a sheep farm (Mooka Station, covering
ca 700,000 acres) located on the west side of the Kennedy Range
about 100 miles inland from the coastal town of Carnarvon and
600 miles north of Perth, the capital of Western Australia. According
to locals, the Aboriginal word "mooka" means "running
waters," but the rock consists principally of the remains
of tiny marine organisms known as radiolaria, countless
numbers of which were deposited as sediment in the shallows near
the shore of an ancient sea. These organisms possessed an unusual
skeletal structure of opaline silica, so when the sea retreated
the sediments were cemented into solid rock by silica (in groundwater)
originating from the radiolaria themselves (and/or possibly from
weathered rocks nearby). This is borne out by the fact that the
best material has properties similar to chalcedony, and generally
occurs as nodules lying in decomposed radiolarian clay beneath
the bed of the creek.
Turritella (a fossiliferous limestone
found in Texas and California) was named by rock hounds after
the silicified shells it contains - tightly coiled. elongated
spiral cones from sea snails of the genus Turritella (these snails
originated in the Cretaceous period, 145 to 65 million years ago,
and are still widespread in today's oceans). However, most of
the "turritella" now available in the US comes from
an area in the Green River Formation south of Wamsutter in Sweetwater
County, Wyoming; it displays amber gold or blue to gray shell
outlines on a dark brown to grayish black matrix, as in the top
two cabs in the left pic. And recently, paleontologists have determined
that this Wyoming sedimentary rock was deposited at the bottom
of an ancient freshwater lake some time in the Eocene (between
53 and 42 million years ago), and that the fossil shells it contains
are really from the freshwater genus Elimia (still abundant in
shallow lakes and streams throughout North America; the shells
of tiny freshwater shrimp often are visible as well). I'm not
sure where the bottom three cabs in the left pic are from, although
they may have been cut from (true) white Turritella limestone
found in the Rocky Cedar area near Elmo, Texas. The cabs in the
right pic are definitely a true turritella (also called crawstone),
found in a remote part of the Baja Peninsula near the town of
El Rosario, Mexico; in addition to turritellids (but from the
Pliocene, ie, ca 18 million years old), the shells of clams and
a horn coral called Flabellum also can be seen. (Among other famous
turritellid stones are one with a white to tan matrix that comes
from an area near Bordeaux, France, and a Miocene sandstone packed
with turritellids from an area called the Erminger Turritellenplatten
near the German city of Ulm.)
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