Pyrite Shapes

[Roz]

Attached are some pics of pyrite I found while in Arkansas. (group shot) The

single piece I found in Texas. I was wondering why the AR pyrite is such weird shapes?

[Guest Nicholas]

Those are really cool! Something I would add to my collection.

[Guest solius symbiosus]

I was wondering why the AR pyrite is such weird shapes?

All of the Pyrite I find in Ky is very similar to the shape of the latter pic. I think that I remember that it forms in a reducing environment. Probably those xls formed over a relatively long time during diagenesis?

[Mike Owens]

Roz - There are pyrite of various shapes, like Arkansas, here also. I'll have to see if I still have any to show you. The one I have posted in the gallery is spherical like yours, but has a different pattern. Is yours from Ellis, Tarrant or Dallas County? - Mike

[Guest N.AL.hunter]

I just posted something in one of the other strings about storing chalcopyrite/pyrite. I once heard or read that this stuff decays releasing some form of weak sulfuric acid and that it can destroy other items it is in contact with. Not sure of the truth in this, but thought I would say something and see if anyone knows the truth. Those pyrite/chalcopyrite nodules are all over the Selma Chalk formation in west Alabama and east Mississippi. Some of them are as large as 2 lbs. But most are smaller, golf ball size.

[Roz]

Yes, the roundish is from Ellis County..

N.AL. Hunter , there is huge truth to what you mention. I had a huge box of pyrite/marcasite from AR. I had most of it stored together in a box. Some pieces had white areas on them. When I looked in the box months later, all were coated with the white. My guess is pyrite disease. All I had left were small pieces that I had stored in a different place. Some of it I had put in oil, as I read somewhere that would protect it. Don't know if that is even true though.

[Rain1950]

As you can see on some specimens, they do form cubes, but sometime the cubes become modified into what are called pyrithedrons. Pyrite will also replace organcis materials such as pieces of wood, so they take on the shape of the material. Pyrite also forms acicular, forming what are called pyrite suns

Pyrite Sun

As with all minerals; Nature is not perfect and each sample will never be pure (unless man-made in controlled conditions). There is always minute traces of other elements present; depending upon the environment where it grows. Note the wide variety of color in agates; each due to trace elements. Sometimes these very trace elements are the cause of things like 'pyrite disease. The environment of origin and those trace elements.

Pyrite disease is caused by sulfur eating bacteria. Most museums recommend soaking the specimens in a sodium azide solution to kill the bacteria and then removing all sulfates with acidification and neutralization. The treatment has to be repeated periodically since it is almost impossible to destroy all the microbes, and they tend to reappear over time. Problem, of course, is that many specimens cannot withstand the treatment.

Who'd a thunk my mineral knowledge would be useful in a fossil forum?

[Roz]

Who'd a thunk my mineral knowledge would be useful in a fossil forum?

Me, for one!

Do you know where one buys azide? Hardware store?

[Rain1950]

[qoute]

Do you know where one buys azide? Hardware store?

INTRODUCTION

Sodium Azide, NaN3, mol wt 65.02, CAS Number 26628-22-8, is a colorless, odorless, crystalline solid (salt-like) or solution. It is soluble in water or liquid ammonia, slightly soluble in alcohols, and insoluble in ether. It is highly toxic and presents a severe explosion risk when shocked or heated. When heated from 275 to 330°C in dry air, the solid crystals decompose with the evolution of nitrogen gas, leaving a residue of sodium oxide. Sodium hydroxide then forms in moist air. Synonyms and Trade Names are Azide, Azium, and Sodium salt of hydrazoic acid.

PROPERTIES

Sodium azide is a common preservative of samples and stock solutions in laboratories and a useful reagent in synthetic work. It is not explosive except when heated near its decomposition temperature (300°C) or reacted with metals; heating sodium azide should be avoided. Sodium azide (solid or concentrated solution) should never be flushed down the drain since this practice can cause serious incidents when the azide reacts with lead or copper in the drain lines and explodes. Sodium azide has high acute toxicity as well as high toxicity to bacteria in water treatment plants.

Note that metal shelves and other metal items used to handle sodium azide (i.e., spatulas) can also result in the formation of heavy metal azides and thus should be avoided. Solutions of sodium azide do not pose the danger of shock-sensitivity associated with the solid form; however, the hydrazoic acid generated when the sodium azide is dissolved is extremely toxic. Therefore, the solution is should prepared inside a laboratory chemical hood. If not dissolved, solid sodium azide should be stored in a secured cabinet because of the shock hazardous.

HAZARDS

Sodium azide is on the Hazardous Substance List because it is cited by ACGIH, DOT, NIOSH, HHAG, DEP, and EPA (see Laboratory Chemical Hygiene Plan section 5 for glossary of terms). This substance also is on the Special Health Hazard Substance List because it is a mutagen. Mutagens may have a cancer risk. All contact with this substance should be reduced to the lowest possible level.

Sodium azide and hydrazoic acid (HN3, which is formed from NaN3 in water) are known to produce hypotension (low blood pressure) in laboratory animals and humans, and to form strong complexes with hemoglobin, and consequently block oxygen transport in the blood.

Acute inhalation of HN3 vapor by humans results in lowered blood pressure, bronchitis, eye, nose, throat, and lung irritation, headache, weakness, and collapse. A skin designation has been assigned to the OSHA PEL due to the ability of NaN3 to readily penetrate intact skin, and any dermal exposure can significantly contribute to the overall exposure to sodium azide.

Target organs are eyes, skin, lungs, central nervous system, cardiovascular system and kidneys. Use appropriate ventilation (laboratory chemical hood) and personal protective equipment (such as gloves) to minimize potential exposure.

WORKPLACE EXPOSURE LIMITS

NIOSH: The recommended airborne exposure limit is 0.11 ppm as hydrazoic acid or 0.3 mg/m3 as sodium azide, which should not be exceeded at any time.

ACGIH: The recommended airborne exposure limit is 0.11 ppm as hydrazoic acid or 0.29 mg/m3 as sodium azide (0.1 ppm Ceiling, Skin), which should not be exceeded at any time.

The above exposure limits are for air levels only. When skin contact also occurs, you may be overexposed, even though air levels are less than the limits listed above.

HANDLING AND STORAGE

* Prior to working with sodium azide you should be trained on its proper handling and storage. Use appropriate personal protective equipment such as safety glasses, goggles, gloves, and laboratory coat when handling sodium azide.

* On contact with water, sodium azide forms hydrazoic acid which is toxic.

* Sodium azide reacts with heavy metals (such as silver, gold, lead, copper, brass, or solder in plumbing systems); and metal salts to form an accumulation of the highly explosive compounds such as lead azide and copper azide.

o Sodium azide is not compatible with chromyl chloride, hydrazine; bromine; carbon disulfide; dimethyl sulfate; and dibromomalonitrile; strong acids (such as hydrochloric, sulfuric and nitric); and acid chlorides.

o A danger of explosion exists from friction, heat or shock.

o Store in tightly closed containers in a secured, cool, and well-ventilated area away from water

Proably not!

[Roz]

Sounds a bit dangerous..

Guess I had better pass on trying to get it

[Roz]

I just thought of something, I think someone may have mentioned

soaking pyrite in vinegar, not on this forum. Has anyone tried that

with success?

[Rain1950]

I just thought of something, I think someone may have mentioned

soaking pyrite in vinegar, not on this forum. Has anyone tried that

with success?

That may help remove the sulphates, but would do nothing to the bacteria

[Roz]

Thanks Rain

[ayahuang]

some indonesians pyrites

[Guest solius symbiosus]

The only thing that I find around here are cubes, but on occasion unusual sulfides.

[Roz]

Since I think some of you know your minerals, you probably know

your rocks. I found these in a recent hunt (where I found the large chunk of coral).

The first (the small gray rocks), maybe gypsum but don't usually see it in that

form? Usually gypsum is the flat pieces that look like glass. How I know them anyway.

A very small oyster next to the rocks.

The next rocks, I just don't know, but am hoping someone knows what they are..

Those white and pinkish are the same type coming out of the side of the banks.

Same kind as the pink and white, in case they are hard to see.

[Bill]

Hi Roz,

The first pic could be Selenite, a crystaline form of Gypsum, or Calcite. Can you easily scratch it with your finger nail? If yes, it's Selenite. If not it's Calcite, which is what it looks like to me.

The others are Gypsum.

[jax]

Heres my pyrite. These are the coolest pieces I have. I also have some nodules that have pyrite running thru them. I'll have to get some pics of those.

[jax]

THese are nodules that I find that have pyrite running thru them. I usally find them near septarian nodules.

[Roz]

Hi Roz,

The first pic could be Selenite, a crystaline form of Gypsum, or Calcite. Can you easily scratch it with your finger nail? If yes, it's Selenite. If not it's Calcite, which is what it looks like to me.

The others are Gypsum.

It is selenite cause it scratched easily... Gypsum sure has a lot of forms. I didn't realize that the desert rose is gypsum. The forms sure do not resemble each other at all.

Always like to know what things are

Thanks, Bill

[Roz]

Heres my pyrite. These are the coolest pieces I have. I also have some nodules that have pyrite running thru them. I'll have to get some pics of those.

I have some small ones with pyrite also, although yours sure look thicker... always great to find those!

[Roz]

some indonesians pyrites

Right there is why I love pyrite, look at the shine!

[jax]

I have some small ones with pyrite also, although yours sure look thicker... always great to find those!

They came from dallas. I believe its Britton Shale. I was shocked to find them

[dr heckle]

yeah i love pyrite ive got a chunk at home the size of a fist ill post a pic asap while im at it ill post a pic of my newly acquired pyritized paraspirifer