Pyritized fossil from Nepal

My friend brought back the most awesome fossil I have ever seen. I admit fossils are not my thing, but this one I like. It is awesome for many reasons. First, he found it hiking in Nepal on a gap year during his college years. Randomly found it on the trail in one of the most exotic places in the world. He knew I would like it. He knew me well because I have kept it all of these years and all the different places I have lived.

Here are the facts from Alden at about.com.
Many fossils, especially seashells in young rocks, undergo some recrystallization in groundwater. In others their substance is dissolved, leaving open space (a mold) that is refilled with minerals from their surroundings or from underground fluids (forming a cast).
Ammonoids were a very successful order of sea creatures (Ammonoidea) among the cephalopods, related to the octopuses, squids and nautilus.
Paleontologists are careful to distinguish the ammonoids from the ammonites. Ammonoids lived from Early Devonian times until the end of the Cretaceous Period, or from about 400 million to 66 million years ago. Ammonites were a suborder of ammonoid with heavy, ornamented shells that thrived starting in the Jurassic Period, between 200 and 150 million year ago.
Ammonoids have a coiled, chambered shell that lies flat, unlike gastropod shells. The animal lived at the end of the shell in the largest chamber. The ammonites grew as large as a meter across. In the wide, warm seas of the Jurassic and Cretaceous, ammonites diversified into many different species, largely distinguished by the intricate shapes of the suture between their shell chambers. It is suggested that this ornamentation served as an aid to mating with the right species. That would not help the organism survive, but by ensuring reproduction it would keep the species alive.

All the ammonoids died at the end of the Cretaceous in the same mass extinction that killed off the dinosaurs.

Charlotte from the mountain Kingdom website/blog writes,"The nearby Kali Gandaki River is a source of black ammonite fossils, known as saligrams, which are considered holy emblems and worshipped as manifestations of Vishnu."

Maybe this is where he got the fossil. How cool is that for rock enthusiasts to find fossils and have them be sacred too! I read that you are not supposed to break open the fossils. Oh well, I think this one was opened up or found this way.
A writer on ECS Nepal website wrote this about a winter trek."Finding some black ammonites were our third nature quest. We searched for them in the Kali Gandaki river bed but determined that we would have better luck in summer or fall, when the river is fuller and washes new (old) fossils out of its banks. Pilgrims believe the fossils to be a sure sign of Vishnu’s presence. Saligrams are the remnants of an extinct form of cephalopod mollusk with a coiled, flat chambered shell. They lived in and left their remains under the prehistoric Sea of Tethys that existed before the slow continental collision that created the Himalayan uplift that gradually joined the Indian subcontinent to Tibet. According to geologists the Muktinath ammonites date from 140 to 165 million years ago. They are also found in north India and southern Tibet, but those around Muktinath are particularly abundant, well preserved and relatively easy to find.

Before we left the Vishnu Mandir, we saw a stone pillar said to have been erected by Jang Bahadur Rana in the 19th century. Narendra interpreted the inscription on it, to the effect that breaking open the fossils is (or was, in those days) punishable by having your hands cut off! Regardless of his ruling, saligrams are for sale, both whole and broken, at Muktinath and Jomsom, Pokhara and Kathmandu, by two-handed shopkeepers."
Here is more info from gwydire.co.uk website about fossils."In India, ammonites found in the valley of the Gandaki River in Nepal and northern India are called Saligrams. They are considered the direct symbol of Lord Vishnu, as one of Vishnu's avatars (incarnations) was stone (Sri Saligram). Saligrams have markings called 'chakras', resembling the discus held in one of the six hands of the god Vishnu. Vishnu's chakra is a Hindu symbol of absolute completeness, with the eight spokes indicating the eightfold path of deliverance. The radial chakra markings in saligrams are actually the ribs of the ammonites. The stones are kept in temples, monasteries and households as natural symbols of Vishnu and water in which they have been bathed is drunk daily. In addition, saligrams are used in marriages, funerals and house-warmings. If a dying person sips water in which a saligram has been steeped, it is believed that they will be freed from all sins and will reach the heavenly abode of Vishnu. You are not allowed to buy a saligram as they are priceless, although they can be supplied if a donation is made. Saligrams are mentioned in Sanskrit texts dating back to the second century BC. .

This description is from the Oregon University,"Ammonite and nautiloid fossils have been prized from antiquity for their mesmerizing logarithmic spiral. In Hindu religion they are held sacred as saligram (a Nepali example is included here), a reminder of the unfolding of the universe by Lord Vishnu the creator. They are the shells of extinct cephalopods, related to the modern pearly nautilus. Ammonites and nautiloids are prized by paleontologists because they were widespread on the world's oceans, and evolved rapidly. Even with the great array of geological dating techniques now available, geological age can still be determined more accurately by a single ammonite than by geochemical methods. These ammonites and nautiloids are from the recently acquired Retallack collection. Photography by Win McLaughlin, text by Greg Retallack, and web development by Keith Hamm. Images © Museum of Natural and Cultural History."
I also attached a photo of an example from the same website and another saligram from a stock photo.
I can't believe that is what I have had around the house for all these years.
My photos are the two photos with Japanese yen for scale.

Labradorite

My second sphere was labradorite. I have been a big fan of this mineral ever since. Apparently the rest of the mineral/ gem world agrees since I see this mineral everywhere at the rock shows. This sphere was not the most colorful but I guess I was a trend setter since this was rather rare in the Mid-1980's and the steep price reflected that rarity. I have since collected many samples with the carved bear twinning being the most spectacular. Who would imagine the crazy colorful labradorite is in the most common family of feldspars!
Here are the facts from Alden at about.com.
Feldspars are a group of closely related minerals that together are the most abundant mineral in the Earth's crust. A thorough knowledge of the feldspars is what separates geologists from the rest of us.

How to Tell Feldspar

Feldspars are hard minerals, all of them with a hardness of 6 on the Mohs scale. This lies between the hardness of a steel knife (5.5) and the hardness of quartz (7). In fact feldspar is the standard for hardness 6 in the Mohs scale.

Feldspars usually are white or nearly white, though they may be clear or light shades of orange or buff. They usually have a glassy luster.

Feldspar is what's called a rock-forming mineral, very common and usually making up a large part of the rock. In sum, any glassy mineral that's slightly softer than quartz is very likely to be a feldspar.

The main mineral that might be confused with feldspar is quartz. Besides hardness, the biggest difference is how the two minerals break. Quartz breaks in curvy and irregular shapes (conchoidal fracture). Feldspar, however, breaks readily along flat faces, a property called cleavage. As you turn a piece of rock in the light, quartz glitters and feldspar flashes.

Other differences: quartz is usually clear and feldspar is usually cloudy. Quartz appears in crystals more commonly than feldspar, and the six-sided spears of quartz are very different from the generally blocky crystals of feldspar.

What Kind of Feldspar?

For general purposes, like picking granite for a countertop, it doesn't matter what type of feldspar is in a rock. For geological purposes, feldspars are quite important. For rockhounds without laboratories, it's enough to be able to tell the two main types of feldspar, plagioclase (PLADGE-yo-clays) feldspar and alkali feldspar.

The one thing about plagioclase that's usually different is that its broken faces—its cleavage planes—almost always have fine parallel lines across them. These striations are signs of crystal twinning. Each plagioclase grain, in reality, is typically a stack of thin crystals, each with its molecules arranged in opposite directions. Plagioclase has a color range from white to dark gray, and it's typically translucent.

Alkali feldspar (also called potassium feldspar or K-feldspar) has a color range from white to brick-red, and it's typically opaque.

Many rocks have both feldspars, like granite. Cases like that are helpful for learning to tell the feldspars apart. The differences can be subtle and confusing. That's because the chemical formulas for the feldspars blend smoothly into each other.

Feldspar Formulas and Structure

What is common to all the feldspars is the same arrangement of atoms, a framework arrangement, and one basic chemical recipe, a silicate (silicon plus oxygen) recipe. Quartz is another framework silicate, consisting only of oxygen and silicon, but feldspar has various other metals partly replacing the silicon.

The basic feldspar recipe is X(Al,Si)4O8, where X stands for Na, K or Ca. The exact composition of the various feldspar minerals depends on what elements balance the oxygen, which has two bonds to fill (remember H2O?). Silicon makes four chemical bonds with oxygen; that is, it's tetravalent. Aluminum makes three bonds (trivalent), calcium makes two (divalent) and sodium and potassium make one (monovalent). So the identity of the X depends on how many bonds are needed to make up the total of 16.

One Al leaves one bond for Na or K to fill. Two Al's leaves two bonds for Ca to fill. So there are two different mixtures that are possible in the feldspars, a sodium-potassium series and a sodium-calcium series. The first is alkali feldspar and the second is plagioclase feldspar.

Alkali Feldspar in Detail

Alkali feldspar has the formula KAlSi3O8, potassium aluminosilicate. The formula actually is a blend ranging from all sodium (albite) to all potassium (microcline), but albite is also one endpoint in the plagioclase series so we classify it there. This mineral is often called potassium feldspar or K-feldspar, because potassium always exceeds sodium in its formula. Potassium feldspar comes in three different crystal structures that depend on the temperature it formed at. Microcline is the stable form below about 400° C. Orthoclase and sanidine are stable above 500° C and 900° C, respectively.

Outside the geological community, only dedicated mineral collectors can tell these apart. But a deep green variety of microcline called amazonite stands out in a pretty homogeneous field. The color is from the presence of lead.

The high potassium content and high strength of K-feldspar make it the best mineral for potassium-argon dating.

Alkali feldspar is a crucial ingredient in glass and pottery glazes. Microcline has a minor use as an abrasive mineral.
Alkali feldspar has the general formula (K,Na)AlSi3O8, but varies in crystal structure depending on the temperature it formed at. The formula actually is a blend ranging from all sodium (albite) to all potassium (microcline), but albite is also one endpoint in the plagioclase series so we classify albite there.
This mineral is often called potassium feldspar or K-feldspar, because by definition potassium always exceeds sodium in its formula. It comes in three different crystal structures that depend on the temperature it formed at. Microcline is the stable form below about 400° C. Orthoclase and sanidine are stable above 500° C and 900° C, respectively. Being in a plutonic rock that cooled very slowly to yield these large mineral grains, it's safe to assume that this is microcline.

In the field, workers generally just write down "K-spar" and leave it at that until they can get to the laboratory. Alkali feldspar is generally white, buff or reddish and is not transparent, nor does it show the striations of plagioclase. A green feldspar is always microcline, the variety called amazonite.

Plagioclase in Detail

Plagioclase ranges in composition from Na[AlSi3O8] to Ca[Al2Si2O8]—sodium to calcium aluminosilicate. Pure Na[AlSi3O8] is albite, and pure Ca[Al2Si2O8] is anorthite. The plagioclase feldspars are named according to the following scheme, where the numbers are percentage of calcium expressed as anorthite (An):

Albite (An 0–10)
Oligoclase (An 10–30)
Andesine (An 30–50)
Labradorite (An 50–70)
Bytownite (An 70–90)
Anorthite (An 90–100)
The geologist distinguishes these under the microscope. One way is to determine the mineral's density by putting crushed grains in immersion oils of different densities. (Albite's specific gravity is 2.62, anorthite's is 2.74, and the others fall in between.) The really precise way is to use thin sections to determine the optical properties along the different crystallographic axes.

The amateur has a few clues. An iridescent play of light can result from optical interference inside some feldspars. In labradorite it often has a dazzling blue hue called labradorescence. If you see that it's a sure thing. Bytownite and anorthite are rather rare and unlikely to be seen.

An unusual igneous rock consisting of only plagioclase is called anorthosite. A noteworthy occurrence is in New York's Adirondack Mountains; another one is the Moon.
Plagioclase means "slanted breakage" in scientific Latin. The play of light in large grains is also distinctive, resulting from optical interference inside the mineral. Both oligoclase and labradorite show it, and in the latter it often has a dazzling blue hue called labradorescence.

The igneous rocks basalt (extrusive) and gabbro (intrusive) contain feldspar that is almost exclusively plagioclase. True granite contains both alkali and plagioclase feldspars.

Onyx

My first rock sphere was an onyx specimen. The way this specimen is cut makes a circle and a v-shaped band. Based on the info below, onyx is banded linearly while agate's bands are curved.
Here are the facts from about.com's geology guy, Alden.
Onyx is composed of chalcedony, with straight bands of color instead of the curved forms typical of agate. So if true onyx is a banded chalcedony, a marble with the same appearance should be called banded marble instead of onyx marble, and certainly not alabaster, which is not banded at all.
Chalcedony is the special name for quartz with microscopically small crystals. Unlike quartz, chalcedony does not look clear and glassy but translucent and waxy; like quartz it is hardness 7 on the Mohs scale. Unlike quartz it can take on every color imaginable. An even more general term, encompassing quartz, chalcedony and opal, is silica, the compound silicon dioxide (SiO2).
The major rock type that is defined by the presence of chalcedony is chert. Chalcedony also very commonly occurs as a mineral filling veins and openings, like in geodes and thunder eggs.

Rhodochrosite

My parents got this from Earth Resources around graduation time. Again, great color.
Andrew Alden from about.com facts below.
Rhodochrosite is a cousin of calcite, but where calcite has calcium, rhodochrosite has manganese (MnCO3).)
Rhodochrosite is also called raspberry spar. The manganese content gives it a rosy pink color, even in its rare clear crystals. Rhodochrosite can have a banded habit, but it also takes the botryoidal habit. The crystals of rhodochrosite are mostly microscopic. Rhodochrosite is far more common at rock and mineral shows than it is in nature.

Malachite!!!!

I love this mineral. You can't get a cooler color-green. The large block of malachite was from Earth Resources in Appleton, WI. It was my first mineral specimen I ever bought. The cost was $25 and I used my birthday money from Grandpa.
The other mineral samples are from a gem and mineral show at a local fair grounds a few years ago in the mid 2000's.
The carved turtle is one of the kids picks from the show.
Here are the facts from about.com's geology guy.
Malachite forms in the upper, oxidized parts of copper deposits and commonly has a botryoidal habit. The intense green color is typical of copper (although chromium, nickel and iron also account for green mineral colors). It bubbles with cold acid, showing malachite to be a carbonate.
You'll usually see malachite in rock shops and in ornamental objects, where its strong color and concentric banded structure produce a very picturesque effect. This specimen shows a more massive habit than the typical botryoidal habit that mineral collectors and carvers fancy. Malachite never forms crystals of any size.

The blue mineral azurite, Cu3(CO3)2(OH)2, commonly accompanies malachite.

Banded Iron Formation from Jasper Knob in the UP of Michigan

This is still my favorite rock of all time. My husband and I collected this specimen in the mid-1980's on a field trip with our geology professor Dr. Palmquist. When we got back to the lab, my husband ground it down on two sides to see the banding. The photos do not do this rock justice.
The following facts are from the about.com geology guy.
Banded iron formation was laid down some 2.5 billion years ago during the Proterozoic Eon. It consists of black iron minerals and red-brown chert. During the Proterozoic, the Earth still had its original atmosphere of nitrogen and carbon dioxide. That would be deadly for us but it was hospitable to many different microorganisms in the sea, including the first photosynthesizers. These organisms gave off oxygen as a waste product, which immediately bonded with the abundant dissolved iron to yield minerals like magnetite and hematite. Today banded iron formation is our predominant source of iron ore. It also makes beautiful polished specimens.

Why did I start this blog?

I have been collecting rocks since I was about 9 years old. The first specimen I collected  was a dark olive green color, almost black. It was full of air holes like empty bubbles, about the size of a volleyball, and very light in weight.  I found this huge specimen in the woods near my house where I grew up in Pennsylvania.  My specimen was not as colorful as this picture below, but the holes and texture are identical.

 I did not believe my Dad when he said it might be industrial slag. No, I thought it was a meteorite or at least some volcanic rock.  My imagination went wild with ideas of how this specimen was formed, where it came from.  I fell in love with the mystery of its origins.
Yes, my Dad was right.  In hindsight, now I know it was industrial slag dumped up in a clearing in the woods.  Over the years, I have lost this first specimen.  However, I have been picking up rocks wherever I have traveled for the past 40 years.  I went to college to study geology based on this fascination with rocks. I learned about how the earth was formed, how the plates move, and my favorite, how to identify rocks and minerals.  Just recently, as I thought of why I love quilting so much, I remembered my petrology class and the colorful thin sections of rocks we used in the microscopes.  It was always about the colors and forms, both with rocks and with fabric and quilting.

I have started photographing all my specimens picked up on geology field trips, on travels, or bought at a gem and mineral show at a local fair grounds.

The "Rocks and minerals rock" blog will be a show case for the beautiful rocks in my collection.