The term pseudomorph, abbreviated ps or pseudo, means “false form.” This two-part article will describe a wide variety of minerals and fossils that have changed from their original form to something else and how that happens. Every good collection should have examples of common pseudomorphs.
The keyword, when discussing “pseudos,” is change. Minerals crystallize and exhibit a particular shape or crystal form. Such things as solution Ph, temperature, pressure, the richness of the solution, even location all play a role in crystallization. Some minerals, once formed, are unstable, so changes also occur as conditions change.
One typical example of a pseudomorph is iron rusting to iron oxide. The original shape remains but not the properties. Iron sulfide pyrite can also change, altering to hydrous iron oxide goethite. When pyrite changes to goethite, it retains the original crystal form of a cube or octahedron but is no longer brassy pyrite but dull dark brown goethite. Goethite after pyrite is a common form of a pseudomorph process called replacement.
Replacements are substances in which the original entity is slowly replaced molecule by-molecule with a new substance while preserving the original form. Other forms of pseudomorphs include casts, paramorphs, and epimorphs. Plus, pseudomorph change scan happen in fossils as well as minerals.
A common example of a replacement pseudomorph in fossils found all over the world is petrified wood. This replacement pseudomorph forms when silica-rich water slowly invades and replaces wood that is quickly buried to avoid rotting. The wood is best preserved or petrified when buried in silica-rich volcanic ash. Arizona has the world’s finest example of this process in Petrified Forest National Park. The huge colorful stone logs present in this park are replacement pseudos as their wood cells are perfectly preserved in their original structure. These solutions carry trace amounts of iron oxide, manganese oxide, and even colorful uranium compounds, which create Arizona’s lovely gem-quality petrified wood.
The specific petrified wood deposit in Arizona formed eons ago when giant trees were felled in some distant place then carried and deposited by fast-flowing waters losing their limbs in the process. Once in place, they were quickly buried by nearby volcanism and the silica-rich volcanic ash, given time, slowly replaced the wood cells with silica minerals. Now Arizona’s petrified wood is the state’s official gem.
Fossilized wood is not the only replacement type of fossil. We find perfectly preserved stone or pyrite ammonites and shells in many limestone deposits, perfect images of the original hard parts. Dinosaur bones we unearth, reassemble and display are replacement fossils. The most unusual dinosaur bone I’ve seen is a massive leg bone, which had been cut in half to reveal the original soft tissue replaced by lovely banded agate.
IDENTIFYING CASTS FROM PARAMORPHS
Continue reading your story on the app
Continue reading your story in the magazine
Filling an Empty Space and Enhancing a Cabochon
I often look for a special feature within a slab when choosing the shape to cut into a cab.
Pterodactyls No Longer Birds of a Feather?
For a couple of decades now, feathered dinosaurs have been all the rage.
The Saga of COLORADO GOLD - 53 Million Troy Ounces and Counting
Colorado has been mining gold even before the region became a territory and is still mining it today.
SPECTACULAR NATIVE SILVER - Rarer Than Gold in Specimen Form
When it comes to naturally occurring precious metal specimens on Earth, finding native silver is not as easy as finding native gold.
PEARL OF THE PACIFIC - San Diego's Pacific Rim Park
Did you know, the Pearl of the Pacific was created in 1998 as a symbol of friendship and unity between the United States, Mexico, China and Russia?
POPULAR PSEUDOMORPHS - More Common Varieties Enhance Any Collection
In part one of this two-part series, which appeared in the December 2020 issue of Rock & Gem, we explained pseudomorphs as minerals whose normal form has changed, so they may look like the original but are now another mineral.
New Era Gems - CARVING A PATH AND CREATING A LEGACY
Think back to your 20th birthday; what were you doing? How did you celebrate?
DIAMONDS - A Luxury Gem Steeped in Fact & Fable
The diamond is one fabled gemstone! For example, google “Hope Diamond” to see all the legends associated with just this one stone said to bring misfortune to its owners.
Cleaning Without Chemicals
Do you have specimens like desert roses, quartz crystal clusters, or geode halves that sat for eons in the open before being collected?
Black Ilmenite and “Titanium White”
The bright-white color that we see in everything from highway lines, donut icing, and tooth-paste to paint, paper, plastics, and ceramics comes mostly from titanium dioxide, the world’s most widely used pigment.
Judge-ing by 2020, the future is bright
G-MAN ON THE G-MEN
HOME ON THE ROAD
Latest bizarre twist relocates 49ers to Arizona
SHHH – IT'S A SECRET!
Arizona Undertakers Marathon
My plan for the classic Dodge Power Wagon I don't own
My mind often springs to life and engages full throttle in the middle of the night when it should be sleeping. When this happens, my brain is like a 4x4 high-centered on a rock, engine revving, all four tires spinning, but no movement. Thank goodness for my pal the iPad. I simply fire up the rectangular electronic wonder and look at 4x4 stuff on the interwebs until sleep once again comes to call.
REMINGTON LIMITED EDITIONS
LOCK, STOCK & BARREL
COVID-19 DIDN'T BREAK THE PUBLIC SCHOOL SYSTEM. IT WAS ALREADY BROKEN.
FAMILIES ARE LEAVING TRADITIONAL SCHOOLS IN RECORD NUMBERS FOR PODS, HOMESCHOOLING, CHARTERS, AND MORE.
Latinx activists are closer than ever to flipping the state—if Democrats don’t take them for granted.
Make friends with weirdos in cold Colorado in WASTELAND 3
Long-term success is the goal
It only took two games to see the best and worst of Washington.
AROUND THE NFC WEST
The NFC West division was tough enough already. But after the 49ers and Seattle Seahawks combined for three playoff victories last year — and the Los Angeles Rams also would have advanced to the postseason if the NFL’s new expanded playoff format had been implemented last year — the wild West looks even tougher this year, universally considered as the toughest division in the entire league with the Arizona Cardinals also an up-and-coming team. The NFC West promises to be a veritable battle royale this season, and here’s a look at what’s new and what’s different from last year while reviewing San Francisco’s three divisional rivals moving into the early stages of the 2020 season.