GENUS This Ammonite Placenticeras Intercalare is the fossil of an extinct marine mollusk of the Class: Cephalopoda, Order: Ammonoidea. This species lived during the Late Cretaceous Period, 110 to 65 million years ago when they (along with 4/5s of the life on the planet) were destroyed by cataclysmic events undetermined.
LOCATION Deposited in marine sediments during the Campanian Age, this specimen was discovered in the dark grey pyritic shales of the Bearpaw Formation in what is known as the Blue Zone (the bottom 150 feet of the Arctica Ovata Zone). Approximately 83 million years old, Ammonites from this zone are scarce and are often unsuitable for restoration as they were unprotected by the iron stone concretion common in other fossiliferous zones and are often misshapen or incomplete as a result. They cannot be excavated by mechanized mining methods and must be recovered by hand. Consequently, there are significantly less Blue Zone Ammonites on the market than Ammonites from other zones. This specimen was hand collected along the St. Maryís river of southern Alberta, Canada on the federal reserve lands of the Blood Tribe.
DESCRIPTION Placenticeras Ammonites are highly prized by collectors. They are larger than most Ammonite species found and have a highly complex fractal suture pattern where the chamber walls (septa) expand from a one-dimensional form to become a two-dimensional shell covering.
The Placenticeras Intercalare is believed by many researchers to have been the male of the species and while usually smaller, brighter and more colorful than the female - Placenticeras Meeki - it is also much less common. An identifying feature of the Intercalare are the raised tubercles (colorfully known as nipples) that are evenly spaced in two concentric rings along the spiral from the protoconch out to the edge of the living chamber. These bumps served an ornamental as well as defensive purpose for the animal which was an aggressive predator with the biggest brain of any creature of its time. The tubercles on this specimen show a remarkable three-dimensional rainbow effect.
This specimen measures 18 inches (46 cm) from the tip of the aperture through the umbilicus to the start of the phragmocone, by 13 inches (33 cm) across. It measures 4 inches (10 cm) at itís thickest and the phragmocone is uniformly compressed to an average thickness of 1/4 inch (60 mm). It is about 20% larger than is the average for complete Intercalare recovered from this zone.
CONDITION Virtually every Ammonite that is recovered from the Blue Zone requires reassembly. Before mineralization replaces and strengthens the original organic material of the Ammonite the tectonic pressure of millions of years of marine sediment deposition breaks the fragile shell into dozens (and often hundreds) of pieces. The majority of specimens located are missing significant portions of the fossil and unsuitable for reassembly. Occasionally all the pieces have been contained by the surrounding shale until they are recovered by trained Fossil Excavators.
This specimen is 99% complete and original. Compression is restricted to the inner whorls and is both uniform and aesthetic. The ventral siphuncle (tubular edge) is intact. The reassembly and restoration has been professionally completed with minimal cracking or patching. Approximately 5% of the gem area was replaced with original material from the concretionary negative.
COLOR The Ammonite Placenticeras Intercalare & Meeki found only in the Bearpaw Shales of southeastern Alberta is unique amongst the worlds Ammonite fossils in that it has been preserved by geological and mineralogical processes that have transformed the mother-of-pearl (Aragonite) of the inner shell into a material that has been designated by the International Association of Colored Gemstones (and other international gem organizations) as the precious gem - Ammolite. The gemstone covering of the fossil Ammonite greatly enhances the value to the collector. We fully examine the gem qualities of the specimen in the Gemological Analysis section of this Appraisal.
This specimen shows the full range of spectral colors over itís entire surface area. While Side 1 (aperture to the left) is predominately Red / Green and Side 2 is predominately Green / Blue, both sides display five (5) or more colors in very unusual combinations.
FINISH Gem Grade Ammonite fossils have multiple coatings of high tensile, polishable, UV Resistant Urethane applied to protect from damage and stop the process of oxidization which, if unchecked, eternally attempts to turn the Aragonite into Calcium Carbonate.
This specimen has been hand polished to Gem quality finish. There is no evidence of oxidization, bonding agents or tool marks. The coating is crystal clear without, overspray or runs.
PALEONTOLOGICAL VALUE This specimen is one of the finest examples of the Ammonite Placenticeras Intercalare that has ever come to market and would command top dollar for itís Paleontological significance and rarity. Unique and rare Ammonites of this size and species have a retail value of between $3,000. and $6,000. USD. We appraise this specimen with a Paleontological Value of $5,500. USD.
Gemstone Ammonites having the full spiral shape and complete gem coverage are relatively new to the worlds collector markets. The industry is less than 20 years old and mechanized mining activity for Ammolite gem material produces few gem grade fossils. The fossils uncovered are often not complete or have deteriorated beyond the possibility of restoration. Many are broken up to provide raw material for the manufacture of loose gemstones. The few specimens that are on the market command high prices.
SURFACE AREA If the surface area of the Ammonite is totaled and the value calculated at current rates for AA Grade Ammolite the fossil could have a price exceeding that which any but a few collectors could afford. With most precious gemstones the larger the stone, the higher the per carat rate used in determining the price. One 10 carat diamond is far more expensive than twenty .5 carat diamonds. The same with rubies, sapphires or opals. It is only with Ammolite found on Ammonites that can be as large as two and a half feet across that the gemstone is comparatively less expensive as it increases in size. While the aragonite shell covering is of high enough quality to prepare Ammolite gemstones, the polishing process is less stringent and exacting than is used in the preparation of gemstones destined for high-fashion jewelry.
The entire surface of this fossil is covered with a uniformly thick layer of high grade Ammolite. The surface has been hand-polished to gem standards with few inclusions and minimal patching. The Gradable Surface Area (GSA) used to determine the value of this specimen was 265 sq. inches. Of this total over 95 % was of Gem Quality.
GEM GRADING The grading of Ammolite and Ammonite Shell is summarised in the following chart:
Colors Gemstone Ammonite can be found in any color known in nature and the imagination of man. Or it could have an infinite array of color combinations in every square centimeter. The higher grades will have either a very strong, bright single color or contain a range of bright colors drawn from a color spectrum more vast than a rainbow, while lower grade gemstones will show less vibrant colors in a more limited range. Generally red/green is more common than blue or purple, but there are certain hues, like crimson or violet or gold, derived from any of the primary colors that are very rare and in high demand.
This specimen displays the complete spectrum of color. Side (1) has multiple shades of Red changing into Green with highlights of Blue/Purple. Side (2) tends more to the Blue with patches of red, gold and purple. The compressed phragmocone is multi-hued with rare colors of violet and pink included. Average Color: Full spectrum - D TO W
Iridescence Ammonite shell is comprised primarily of aragonite with trace elements of aluminium, barium, chromium, copper, iron, magnesium, manganese, silicon, strontium, titanium and vanadium. The spectral property of the mineral aragonite that allows us to see the incredible play of colors across its surface is its iridescence. The shell surface is composed of closely-packed, tabular, hexagonal crystals of aragonite oriented with their c-axis vertical to the shell surfaces and united into thin lamellae (plates or scales). The thickness of these lamellae is of the same magnitude as the wavelengths of the spectral colors which make up white light. Thus, when white light (sunlight) enters the regularly-spaced thin layers of aragonite, diffraction occurs, and flashes of spectral colors are seen. As the plates of aragonite crystals vary in thickness with the addition of the trace elements which are randomly arranged and is interspersed with inclusions of organic material (conchiolin) the intensity of the diffracted colors also varies. The best Ammonite shell will have brilliant, vibrant iridescence, continually dancing with changing colors as the angle of the incident light changes.
This Ammonite is one of the most brilliant Gemstone Ammonites yet inspected. The iridescence is strong and bright across virtually the entire surface.
Average Iridescence: B1
Chromatic Shift The color of most Gemstone Ammonites changes dependent on the angle of light entering and the viewers perspective. Sometimes subtle, and sometimes spectacularly dramatic, a chromatic shift occurs. Most red will shift to green and most green will shift blue, etc. This is called dichromatic. Some gem material will have the shift restricted to hues within the same primary color group. This is monochromatic. The best gem material has spectrochromatic shift. Color will shift through the entire spectrum depending on light source and your angle of observation.
Average Chromatic Shift: Spectrochromatic
Rotational Range With the iridescence and chromatic
shift variations some material will not show strong, vibrant colors through
360° degrees of rotation. As the gemstone is rotated the brightness
decreases and darkens to black. This is due to the light wave diffraction
being blocked by the organic inclusions in the aragonite. For a gemstone
to be Graded AA it must show a brilliant color through 360° of rotation.
Average Rotational Range: 360°
GEM VALUE Gemstone Ammonites are priced by adding their paleontological value as a specimen to the total value of the gemstone Ammolite that is on their surfaces.
This specimen has been inspected and Graded and determined to have the following percentage of Gem Grade shell:
AA GRADE - 45 %
- 119.25 sq. in. @ $500./ = $59,625.00 USD
A GRADE - 35 % - 92.75 sq.in. @ $300./ = $27,825.00 USD
B GRADE - 15 % - 39.75 sq.in. @ $100./ = $3,975.00 USD
Total Gemological Value is $91,425.00 USD
ESTIMATED REPLACEMENT VALUE We determine the ERV (or Retail Value ) by adding the paleontological and gemological values. Estimated Replacement Value is the retail price that someone might reasonably pay when buying an object from a dealer or a gallery, or the amount for which one might insure an object.
ERV = PV + GV = $94,937.00 USD
FAIR MARKET VALUE The FMV (or Wholesale Value) is determined by taking the retail price and dividing by 2. The Fair Market Value is the amount someone might receive when selling to a dealer or through an auction service. It is also the value the IRS and Revenue Canada requires for tax calculations and donations to tax-exempt organizations.
FMV = ERV / 2 = $47,468.00 USD
This document is intended for insurance purposes only, being an estimate
of the cost to replace the object at full retail and wholesale prices (sales
taxes not included) in effect at this date. The information recorded on
this appraisal represents our interpretation of the results obtained from
Gemological and Paleontological evaluation and grading techniques designed
for this purpose. Due to the subjective nature of Gemological and Paleontological
Appraisals, results may vary considerably between Appraisers. Objects are
graded, identified and appraised only to the extent that surface examination
allows. We have made this evaluation to the best of our knowledge and ability
but can assume no liability for same, not attributable to gross negligence,
fraud or willful intent.
© 2001 AMMONITE.COM