Dinosaur Fossil Gembone slab cut 1 side 5.2\" 206g Unpolished Utah UT 5792 For Sale

Welcome to PioneerFossils!

A Certificate ofAuthenticity, which has a photo on it of the exact item you purchased, willaccompany the specimen.

Here is somewonderful high-grade Dinosaur Gembone. From a Sauropod. It is a slab that is unpolished. It is cut smooth on one side, and is rough on the other side, ranging in thickness from 3 mm. to 17 mm. (see photos).

It measures about 5.2 inches at the longest measurement, and weighs 206 grams (7.27 oz.).

Wet photos are taken in direct sunlight.

From the MorrisonFormation, probably from Utah along the Utah-Colorado border. From an old collection. These formed during the Jurassic, about 150 million years ago. This is where gembone is found. It is neverCretaceous, and the Morrison Formation (Jurassic) is home to the bestgemstone. Most gemstone is from sauropods,though Allosaurus, Stegosaurus and a few other species can be found.

Gembone is one ofonly 5 recognized gems from living things. The other are pearl, ammolite, jetand amber. It is made from dinosaur bonethat has agatized, and minerals from groundwater are deposited within thebones, where the marrow used to be. Thetrabeculae, which were the spongy partitions in the bone, form a series ofborders around the colored minerals. The trabeculae can be dark or light, ascan the minerals.

The gembone colorsare many. Most (about 95%) are “earthy” colors, such as brown, greys and tans.However, reds, blues, whites, yellows, oranges, etc., are in a small number ofthem (about 5 % of gemstones). These arethe most popular colors. The mineralscausing these colorations include agate, hematite, iron, pyrite, jasper,marcasite, quartz or other crystal or mineral.

Some gemstoneshave interesting patterns. Sometrabeculae “cell walls” resemble spider webs, and are called spider-webgembone, and sell for a premium. Dark trabeculae is usually desired, as itcontrasts well with the colors of the minerals. “Glassiness” and clarity are also important.

The 1998 rarebook, “AMERICAN DINOSAUR The Vanishingof Gembone by Thomas Helfrich”, accurately predicts the increasing rarity andvirtual disappearance of gembone, we are told.That is exactly what has happened. Top grade gemstone is almostimpossible to find in the wild anymore.

That is because ofthe “perfect storm” of events 35 million years ago in today’s MorrisonFormation that allowed gembone to form. Nowhere else in the world, to ourknowledge, did this happen in exactly the same way to achieve these wonderfulcolors. To quote another, The layers on the Colorado Plateau rose up during theTertiary intrusions, about 35,000,000 years ago, when the San Rafael Swell andthe La Sal, Henry, and Abajo Mountains were formed. As these ranges wereforming, local strata layers were flooded with silica-rich, superheatedgroundwater. This provided the appropriate environment to begin the replacementof the calcite in the original fossils with silicates.

We have heardexcellent gembone has increased many times in value in just the last few years.Gemstone looks brighter and clearer when it has been polished. Unpolished gemstone is usually displayed wet,to show how it can look when polished.Our photos will have a “wet” or “dry” note in the photo to eliminatepossible confusion.