POPULAR PSEUDOMORPHS - More Common Varieties Enhance Any Collection
Rock&Gem Magazine|January 2021
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.
BOB JONES 

That change results in pseudomorphs, sometimes called pseudos, including replacements, casts, paramorphs and others. Some of these pseudomorphs are very attractive and common enough to add to any collection.

This article will describe some of the common and attractive pseudomorphs that are most likely available to collect. These examples include minerals and lapidary materials like petrified wood, as described in the first part. The most common lapidary material that can contain pseudomorphs are agates, especially banded agates. We may not think of agates as having pseudos, but many do.

Banded agates form in gas vesicles or openings in volcanic rock. One theory says silica-rich waters invade these open pockets and deposit the silica as alternating bands of color. Another theory suggests silica gel in the still fluid volcanic rock accumulates slowly to form rounded masses that cool, forming agate banding. In either case, the solutions in the cavity also contain molecules of other minerals like carbonates and zeolites, which tend to crystallize first on the walls of the hardening volcanic rock. The formation of the agate bands follows, setting the stage for pseudomorphs to develop.

DYNAMIC DEVELOPMENT

As the still hot silica-rich solution slowly cools, it may replace the already formed carbonate or zeolite crystals. The result is silica ps carbonate or zeolite, which is visible when the agate is cut. Some of these pseudos are hexagonal, most likely a carbonate mineral calcite or aragonite. Several zeolite minerals form as radiating spherules of needle crystals or longer single crystals and can be replaced by silica and develop small radiating shapes attached to the vesicle wall. Silica can change them into pseudos. Another interesting feature in some agates is holes left when long slender needle crystals form, are engulfed by the agate then dissolved away, leaving a tube-like opening or cast.

One of the most common and abundant sources of colorful pseudos is malachite ps azurite found in many desert copper mines. In these deposits, weathering can penetrate to depths of 1,000 feet or more forming secondary minerals. These impure waters, often acidic, attack primary copper minerals like chalcopyrite and the host rock, mostly limestone. Often, a host of copper develops, including azurite, malachite, cuprite, native copper, and chrysocolla. As part of this process, pseudomorphs become inevitable and form copper after cuprite, chrysocolla after azurite, or malachite after azurite, the most common colorful copper carbonate pseudomorph.

The molecular structure of azurite involves three positively charged copper cations, two negatively charged carbonate radicals, and two negative OH radicals. Malachite’s molecular structure is simpler, two copper cations, one carbonate radical, and two OH radicals. Of these two copper carbonates, azurite is slightly less stable. When weathered, it can give a copper atom and a carbonate radical, resulting in it becoming malachite. This change in the chemistry also alters the color, from blue azurite to green malachite, while retaining the original monoclinic crystal form of azurite — which is the most common and most abundant copper mineral collected.

MINING FOR PSEUDOMORPHS

Continue reading your story on the app

Continue reading your story in the magazine

RELATED STORIES

Heart and Soul

Seek renewal and inner peace at Sedona’s L’Apothecary Spa.

4 mins read
Global Traveler
November 2021

Came Through Drippin

Most of the world relies on flood irrigation to water crops. A more efficient alternative hasn’t been widely adopted because it’s so expensive. One Israeli soil physicist has the answer: a tiny plastic widget

10+ mins read
Bloomberg Businessweek
September 27, 2021

The Site Pushing the Big Lie About Arizona's Election Audit

The Gateway Pundit, which has a history of advancing promoting the audit in Maricopa County

3 mins read
Newsweek
August 13, 2021

FAMILIES URGE USING NEW DNA TECH TO ID PEARL HARBOR UNKNOWNS

William Edward Mann enlisted in the Navy after graduating from high school in rural Washington state. A guitar player, he picked up the ukulele while stationed in Hawaii.

5 mins read
AppleMagazine
AppleMagazine #510

Kyrsten Sinema – Shape Shifter

From Green Party rabble-rouser to Senate power broker, Kyrsten Sinema’s rise is a political fairy tale—and nightmare.

10+ mins read
Mother Jones
July/August 2021

America's Friendlist Summits

Some high points require expert skill, a bit of luck, and probably some suffering. Not these. Here are 15 peaks—high on views, low on effort—that don’t play hard to get.

10+ mins read
Backpacker
May - June 2021

“I'm Your Huckleberry” Has a Double Meaning for Old Tucson

Saving the old girl is more than a dream.

6 mins read
True West
April 2021

OVERLAND ADVENTURE 2020: PART 2

Exploring the Gold King Mine and more of Arizona’s historic backcountry

5 mins read
Four Wheeler
May 2021

TAILGATE MAGIC

Dee Zee’s new tailgate cutting board is perfect for overlanding

2 mins read
Four Wheeler
April 2021

INTEL ANNOUNCES ARIZONA EXPANSION AS CHIPMAKER SEEKS FOOTING

Intel announced this week it will build two new factories in Arizona and outsource more of its production as a new CEO looks to turnaround the struggling chipmaker.

2 mins read
AppleMagazine
AppleMagazine #491