Skip to main content
Go to accessibility notice


    "Gem" Ammonite
    Placenticeras costatum
    Late Cretaceous, Bearpaw Formation
    Alberta, Canada

    Ammonites are recognized as mollusks with shells, and these marine invertebrates belong to the cephalopod class. Only living in the outermost chamber, Ammonites continuously "built" new shell as they grew. They were actually predatory and had sharp, beak-like jaws inside a ring of tentacles, allowing them to function as carnivores. As Ammonites moved through the ancient seas, they were propelled by squirting streams of water and using a tubelike structure called a "siphuncle" which siphoned air and regulated buoyancy. All Ammonites went extinct at the end of the Cretaceous Period, at the same time as all of the Dinosaurs, some 65 million years ago.

    This exceptional "gemmy" Ammonite features fabulous colors on both sides with green, red, and gold being the dominant shades. This specimen is rather well inflated which is to be noted since the majority of freestone Ammonites are typically quite compressed. Measuring a robust 10 inches (25.4 cm), this is a sizable example. The shell nacre has been preserved as Ammolite, a bona fide gemstone material certified as such, since 1981, by the World Jewellery Confederation. This extremely bright and colorful Ammonite is a rare example of the costatum species and was mined at the Korite Oxbow Mine which has been closed since the early 2000s. The iridescent shell has sections exhibiting the "dragon skin" pattern in the Ammolite, adding to the character of this particular specimen. These "gemmy" Ammonites are virtually only found in Alberta, Canada.

    This particular specimen is collector grade, without question, and is truly both a fossil and a gemstone. This Ammonite exhibits some indentation and several patches without the colorful shell material, but, overall, the specimen is in good condition and a superb representation of this type of Ammonite. There are even hints of blues and purples on the shell evidencing that it never looks the same twice. The specimen comes with a custom "V" wood stand and a laminated Certificate of Authenticity.
    Overall Measurements: 10.0 x 9.0 x 2.0 inches (25.4 x 22.9 x 5.1 cm)

    Condition Report*: Condition report available upon request.
    *Heritage Auctions strives to provide as much information as possible but encourages in-person inspection by bidders. Statements regarding the condition of objects are only for general guidance and should not be relied upon as complete statements of fact, and do not constitute a representation, warranty or assumption of liability by Heritage. Some condition issues may not be noted in the condition report but are apparent in the provided photos which are considered part of the condition report. Please note that we do not de-frame lots estimated at $1,000 or less and may not be able to provide additional details for lots valued under $500. All lots are sold "AS IS" under the Terms & Conditions of Auction.

    Auction Info

    Auction Dates
    October, 2015
    4th Sunday
    Bids + Registered Phone Bidders: 2
    Lot Tracking Activity: N/A
    Page Views: 2,067

    Buyer's Premium per Lot:
    25% on the first $100,000 (minimum $14), plus 20% of any amount between $100,000 and $1,000,000, plus 12% of any amount over $1,000,000 per lot.

    Sold for: Sign-in or Join (free & quick)

    Heritage membership

    Join Now - It's Free

    1. Past Auction Values (prices, photos, full descriptions, etc.)
    2. Bid online
    3. Free Collector newsletter
    4. Want List with instant e-mail notifications
    5. Reduced auction commissions when you resell your
    Consign now
    • Cash Advances
    • More Bidders
    • Trusted Experts
    • Over 200,000 Satisfied Consignors Since 1976
    Only 6 days left to consign to the 2020 June 25 Asian Art Signature Auction - New York !

    Learn about consigning with us

    The catalogue has some beauties! And your friendship, as well as your excellent work, means a lot too.
    Mara Jayne M.,
    New York, NY
    View More Testimonials receives more traffic than any other auction house website. (Source:

    Video tutorial

    Getting the most out of search