The Copper Scorpion

This story interests me because I am a Scorpio and I love rocks, minerals, gems, fossils, and crystals.  So, when I came across this image on RockSeeker.com I just had to expand on his post. 

The original post is about how a copper scorpion was on display at the 2019 Tucson Gem and Mineral Show and ended up on the AZ MMNRE Museum Twitter page.  But also, about how Scorpion the became entombed and turned into a copper fossil.  Credit: Reddit.com

Pseudomorphism

In mineralogy, a pseudomorph is a mineral or mineral compound that appears in an atypical form, resulting from a substitution process in which the appearance and dimensions remain constant, but the original mineral is replaced by another. The name literally means “false form”

Encrustation Pseudomorphism

According to Tulane University, this phenomenon is known as encrustation pseudomorphism and is defined as, “…a thin crust of a new mineral forms on the surface of a preexisting mineral, then the preexisting mineral is removed, leaving the crust behind, we say that pseudomorphism has resulted from encrustation. In this case the thin crust of the new mineral will have casts of the form of the original mineral.”

Most likely, the doomed scorpion became entombed in the rock. Over time, copper-rich fluids ultimately came into contact with the entombed scorpion, depositing the metal as it evaporated. This process would be similar to how petrified wood is formed.  Another theory as to how the scorpion became a solid piece of copper is simply the result of early and inefficient copper smelting. It’s possible that during the copper smelting process, liquid copper spilled and made its way through the rocks to where the scorpion was entombed.

Other Examples of Pseudomorphs

Pseudomorph of goethite after pyrite – Rob Lavinsky, iRocks.com 5.9 x 5.9 x 5.3cm

Goethite, Pyrite Locality: Pelican Point Area, Utah County, Utah, USA  

An unusually large, striking pseudomorph of goethite that has replaced pyrite crystals. This floater cluster has a fine antique bronze patina. Looks like modern art!

In other fields

Pseudomorphs are also common in paleontology. Fossils are often formed by pseudomorphic replacement of the remains by mineral matter. Examples include petrified wood and pyritized gastropod shells.

https://www.irocks.com/minerals/specimen/49412

Fossils

Provided by Factmonster

Fossils are the remains or imprints of prehistoric plants or animals. They are found in sedimentary rock (rock formed from sand and mud), coal, tar, volcanic ash, fossilized tree sap or frozen in ice. Usually only the hard parts of plants and animals, like their bones and teeth, become fossils.

Most animals that became fossils either lived in water or were washed into a body of water. After an animal died, its soft parts, such as its fur, skin, muscle and organs, decomposed. The hard parts that remained were buried under moist layers of mud or sand, where there was no oxygen and bacteria to cause them to decay. The sediment that covered the bones eventually turned into solid rock. Over the course of millions of years, minerals in the surrounding rock partly or completely replaced the original animal material, forming a fossil.

Sometimes, water seeped into the rocks and dissolved the animal remains. When this happened, the outline of the fossil remained intact between the layers of rock, leaving a fossil in the form of a natural mold.

https://education.nationalgeographic.org/resource/fossil

Paleontologists, scientists who study dinosaurs, use the fossils to learn about the creatures who roamed Earth millions of years ago.

In archaeology, organic pseudomorphs are impressions of organic material that can accumulate on the surface of metal artifacts as they corrode. They may occur when metal artifacts are buried in contact with organics under damp soil.

The image of the scabbard above comes from OF DAGGERS AND SCABBARDS: EVIDENCE FROM ORGANIC PSEUDOMORPHS AND X-RADIOGRAPHY which is an interesting read.

Similar Morphisms

Diamond is a polymorph of the element carbon, and graphite is another. While the two share the same chemistry, C (elemental carbon), they have very different structures and properties. Diamond is hard, graphite is soft (the “lead” of a pencil).

So, diamonds were once pieces of coal that have been transformed under high pressure and temperature, right?

Nope! This is an old wives’ tale, just like “another drink will cure your hangover” or the idea that being out in the cold causes you to catch a cold. Diamonds are actually much older than plants, which are the main ingredient for the formation of coal.  The basic old-fashioned recipe for a diamond calls for:  Carbon deposits, deep within the earth, that are subjected to temperature and pressure.

The exact time that it takes for a diamond to form within the earth is unknown. Some materialize in days, weeks or months. Others take millions of years. Most diamonds are hundreds of millions of years old, with many dating back 1 to 3 billion years. That’s because diamond growth isn’t always a continuous process. A diamond might start to grow, then experience an interruption because of a change in temperature or pressure. It could sit for hundreds or millions of years before growth resumes.

How old are diamonds? A diamond can’t be dated to find out its precise age, but inclusions of other minerals can suggest an estimate. Diamond inclusions that contain specific elements like potassium can be subjected to radioactive dating.

As the diamonds form deep in the earth, they withstand exposure to all sorts of gasses, minerals, and other materials surrounding the ore. Although the budding gem hardens to an unbreakable state, anything it touches during this phase can impact its color. Most diamonds appear white, but upon further inspection, have a yellowish tint or a light, almost imperceptible shade of brown. This doesn’t mean that there is anything “wrong” with the diamonds, just that they’re unique in their beauty.

Natural Diamond is crystal-clear carbon mined from rock called “kimberlite” deep in the Earth.

According to the Journal of Geology Kimberlite, and rocks with kimberlitic affinities, have a relatively wide distribution throughout the United States. They occur in the western margin of the Appalachians from New York to Tennessee; in the central region of the U.S. including Kentucky, southern Illinois, Missouri, Kansas and Arkansas, and in the Western States of Montana, Colorado, Wyoming and the Colorado Plateau. However, diamond-bearing kimberlite is currently known to be present in only two areas, Arkansas and the Colorado-Wyoming State Line.

Coal and Climate – Past and Future

Coal Seam

Coal is found all over the world

Predominantly in places where prehistoric forests and marshes existed before being buried and compressed over millions of years.

Prehistoric Forests?

Wow … So, coal was once plants: trees, bushes, ferns, flowers, and peat.  That’s amazing! 

Coalification

There are four major types (or “ranks”) of coal. Rank refers to steps in a slow, natural process called “coalification,” during which buried plant matter changes into an ever denser, drier, more carbon-rich, and harder material. The four ranks are:

Anthracite: The highest rank of coal. It is a hard, brittle, and black lustrous coal, often referred to as hard coal, containing a high percentage of fixed carbon and a low percentage of volatile matter.

Bituminous: Bituminous coal is middle-rank coal between sub-bituminous and anthracite. Bituminous coal usually has a high heating (Btu) value and is used in electricity generation and steel making in the United States. Bituminous coal is blocky and appears shiny and smooth when you first see it but look closer and you might see it has thin, alternating, shiny, and dull layers.

Subbituminous: Subbituminous coal is black in color and is mainly dull (not shiny). Subbituminous coal has low-to-moderate heating values and is mainly used in electricity generation.

Lignite: Lignite coal, aka brown coal, is the lowest grade coal with the least concentration of carbon. Lignite has a low heating value and a high moisture content and is mainly used in electricity generation.

The precursor to coal is peat.

Peat is a soft, organic material consisting of partly decayed plant and mineral matter. When peat is placed under high pressure and heat, it undergoes physical and chemical changes (coalification) to become coal.

Powder River Basin

The biggest coal deposit by volume is the Powder River Basin in Wyoming and Montana, which the USGS estimated to have 1.07 trillion short tons of in-place coal.

Of the factors involved in coalification, temperature is much more important than either pressure or time of burial. Subbituminous coal can form at temperatures as low as 95 to 176 °F while anthracite requires a temperature of at least 356 to 473 °F.

Although coal is known from most geologic periods, 90% of all coal beds were deposited in the Carboniferous and Permian periods, which represent just 2% of the Earth’s geologic history. Paradoxically, this was during the Late Paleozoic icehouse, a time of global glaciation. However, the drop in global sea level accompanying the glaciation exposed continental shelves that had previously been submerged, and to these were added wide river deltas produced by increased erosion due to the drop in base level. These widespread areas of wetlands provided ideal conditions for coal formation. 

Wildfires

Favorable geography alone does not explain the extensive Carboniferous coal beds. Other factors contributing to rapid coal deposition were high oxygen levels, above 30%, that promoted intense wildfires.

Current Global Warming

“Climate change” and “global warming” are often used interchangeably but have distinct meanings. Similarly, the terms “weather” and “climate” are sometimes confused, though they refer to events with broadly different spatial- and timescales.

Has the Earth been hotter than it is now?

Earth’s global surface temperature has increased by around 1.1 °C compared with the average from 1850–1900—a level that hasn’t been witnessed since before the last ice age, some 125,000 years ago.

125,000 Years Ago?

But Wait … at the beginning of this article it is stated that coal is predominantly in places where prehistoric forests and marshes existed before being buried and compressed over millions of years.

What’s so fascinating about Coal?

What this article is really about is my fascination with Coal.  I love collecting rocks, minerals & gems. 

This is my 10 pound chunk of coal.  To me it is beautiful.

It is part of Earth’s past.  It also makes me think about our future and the cycle the Earth goes through. 

Will someday our beautiful forests, like the Sequoia’s, be coal?

The cycle of our Earth will be in a future post.