The Beauty of Carved Stone

There is so much natural beauty in stone - I enjoy seeing it used to the full extent of its potential.  Going through a museum like the Orsay in Paris provides the opportunity to see stone used a variety of ways.  The floor of the museum is populated with neo-classical sculpture, most of which is pure, opaque, featureless white stone.  The emphasis is on the form of the sculptures, not the color or the material.  But apparently the idea that classical sculpture was colorless is an accident of history.

There is a great deal of evidence suggesting that most ancient Greek and Roman sculptures were painted, gilt, or inlaid with colored stone.  Color was important in the art of that era in a way that is no longer obvious to us.  By the time these ancient sculptures were unearthed in Italy during the Renaissance, much of the color of the statues had been worn away, and any embellishing gemstones had been removed.

Barrias 1899 sculpture "Nature Unveiling Herself to Science" is an example of a "neo-classical" form with polychromy - colors.  This statue is composed largely of marble and onyx.  The onyx forms the off-white folds of Nature's veil, and sweeping red and cream marble forms the drapes of her gown.  The sculpted stone of the gown is skillfully completed to allow the color and pattern of the red marble to look very much like fabric.  The clasp of the gown is a scarab of malachite mounted on a blue belt of lapis lazuli.  The original also apparently had red coral lips and lapis eyes as well.

It can be so easy to take the idea of stone sculpture for granted, given how often such pieces are of a single color.  Using colored stone, and playing on those colors to enhance the piece, makes the art seem so much more real, accessible, and very hard to ignore.

October's Birthstone: Opal

Radiant, colorful opal is the birthstone for October. There are several theories about the origin of the word “opal,” but the most probable is that it is derived from the Sanskrit word upala, which means “valuable stone.”

The aborigines of Australia have an ancient story about how opal was created. The Creator descends to earth, bringing a message of peace to humanity. The Creator’s foot touches the earth, and the rocks in that spot suddenly come to life and begin to glitter in a variety of brilliant colors. Those sparkling rocks became opal.

Most of the world’s opal, 95-97%, is mined in Australia--hence the creation story--with a small amount produced in the Americas. Opal is related to quartz; but unlike quartz, it is not a mineral. It is instead a kind of silica, and is found in various types of rocks. The most commonly found colors of opal are greens and whites, and the red/black combination is the most rare.

Opal’s most notable characteristic--its glittery, colorful radiance--is know as “play of color.” In the 1960’s, scientists discovered that within opal, tiny spheres of silica interrupted the passage of light through the gemstone, causing the light to refract. This answered a question that until then no one could answer--why opal produces the lovely play of color that makes it so popular.

If you’re looking for an alternative for an October birthstone, pink tourmaline is a beautiful choice. Because it is classified as a semi-precious stone, it is more expensive than opal. Tourmaline comes in a variety of colors, including one called “watermelon” which is green on the outside and pink on the inside.



Photographs of Opal by Opals-On-Black
Photograph of Tourmaline Ring by Liverpool Design Festival

Gemstones as Minerals

I am fascinated by minerals.  We so often see gemstones in a final form as faceted stones or polished beads that it can be easy to forget what these substances look like in their native state.  The Lyman Museum in Hilo, Hawaii has a small but excellent collection of minerals.  Each specimen is notable either for size, rarity, or beauty.  Here are a few that particularly caught my eye ...

I spotted a huge, beautiful brown zircon, cubic, almost two inches on a side.  Never seen one that shade or that size.  There was a pyrite sample with the characteristic cubic box shape.  This one had several "boxes" stuck together at the corners, the largest appeared to be about 2.5 inches on a side.  The pattern isn't unusual for pyrite, but this one was smooth and perfect.  The surface of the crystals was shiny and almost mirror-like.

Some of the minerals had colors that surprised me.  There was a flourite sample with colors ranging from orange and burgundy to teal and lime.  A stunning chrysocolla from Arizona was a vibrant, glowing, light blue green.  An azurite sample was a deep, dark midnight blue, and sparkled like stars from reflections off of the facets of hundreds of tiny crystals.  Even the rose quartz was notable.  It was a perfectly uniform gorgeous pink, studded over with crystals.

The collection contained a sample of carved minerals.  This included ones I'd seen before, such as jade, carnelian, and malachite.  But there were other carved items from minerals I haven't seen used this way very often, such as lapis lazuli carved into a statue of a horse, and a head carved from aquamarine.

The petrified wood samples were excellent.  There were not simply small chunks, but full circular cross sections from trees, with rings preserved now as stone.  The process of turning something like a tree into a stone is amazing, and in this case left behind small crystal filled geodes right in the "wood."

Such a wonderful visit is always inspiring.  The next time I pick up a smooth bead of azurite, I will remember the spectacular mineral of midnight blue, with stars flashing. 

The Ancient Lure of Shells

What to blog about today, ten years after 9/11/01?  I remember feeling that life would never be the same, and feeling totally ungrounded and out of touch.  So since then, I have tried to use this day for reflection and connection.  Wondering how I might bring that sensibility here to the blog, I chose to focus on a material that has a strong connection with life, and that has been a part of human culture for millennia - shells.

Shells have been used as jewelry and body adornment since before recorded times.  Shells are numerous, have a vast array of colors and textures, and often can be made suitable for wearing with little effort.  Mother of pearl, the inner lining of certain shells, remains ubiquitous in fashion, both in jewelry and in items like buttons.

My appreciation for shells has expanded very recently after visiting the Lyman Museum in Hilo, Hawaii.  I went primarily to see the mineral collection (more on that in a later post) and found myself enthralled by the amazing collection of shells from pacific marine life.  For some reason, I have always found it easy to forget that shells are a product of living processes.  Living organisms create shells.  They are an incredibly clever answer to a diverse set of evolutionary constraints found by many forms of ocean life.  And the diversity of the constraints and environments has led to an amazing diversity in the shells themselves.

The colors included orange, black, brown, pink, green, ivory, yellow, teal, rose, purple, and burgundy.  Textures were anywhere from smooth, nubbed, and rippled, to rough, sharp and spiked.  Some lovely fluted and scalloped shells were cephalopods, a group that includes squid and octopus.  Another group of shells, gastropods, shared a similar amazing coiled and spiral shape.  Many kinds of shells sport patterns that look like that of leopards and tigers, both in the patterns themselves and in the colors.

One of the more interesting animals was the Xenophora Pallidula.  In Latin this apparently means "bearer of foreigners."  This creature has an initial shell, and then finds other shells and attaches them to itself.  I couldn't help thinking that this was a kind of flattery - a shell using shells for adornment.  Of course, this behavior serves many purposes, and jewelry probably isn't one of them.  But some of the shells-with-shells were very symmetrical, with the additional shells 'glued' on in spiky ridges like a comb.  The beauty of it seemed almost purposeful.

There were thousands and thousands of different shells. It helps to underscore the vastness of the ocean, and the mass of life on Earth.  To me it is an appealing idea, and touching these shells - wearing them - seems like a small but real way to connect with the history of all living creatures on the planet.

Image Credit: wildxplorer, Le Grande CC 2.0, on flikr via Creative Commons

The Color of Stones: Meanings, Uses, Psychology and Fashion

Color is powerful.  Colors are fraught with symbolism, tradition, and psychological influences, much of which we internalize only subconsciously.  Everyone has personal preferences, but none of us can escape the context of our own culture.  This context shapes how we perceive color, and how it fits in as an integral part of our lives.

Gemstones and glass have been chosen and created specifically for their colors for thousands of years.  All forms of personal adornment have included colorful stones, shells, and wood since prehistoric times.  Colors were chosen to convey status, mood, wealth, and other information.  Some stones were only to be used by the ruling class, or in places of worship, because their color was considered sacred.

Today the psychology of color is a major area of research, since it has direct applications in industry, politics, marketing, medicine, sports, education, and just about every other sector of society.  Color can change how we make purchases.  It can change how we cast our vote in elections.  It can make us feel energized, peaceful, or tired.  It can change how we perform in sports and on exams.

One of the primary aspects of gemstone jewelry creation is the use of color, in harmony, unity, or contrast.  Similarly, the buyer of gemstone jewelry makes their choice largely influenced by the color of the piece.  Again, we all have personal preferences, but are likely to move towards pieces that have appeal for a variety of reasons.  For example, white might not be one's favorite color in jewelry, but in western culture most brides choose white pearls for weddings, and sport white diamonds on their fingers.  The context and symbolism of a wedding greatly influences our choice of color.  And the reverse remains true - white gemstones bring up thoughts of weddings, new starts, cleanliness and purity.

So to delve deeper into color, I've been doing a bit of research, and will be posting a series on "The Color of Stones."  I'll be posting about some of the symbolism, studies into color, the nature of chakra points, and some of their interrelationships.  This will give consumers of gemstone jewelry some insight into their own minds - why they choose the colors they do, and conversely, how they can choose colors to enhance their own moods and possibly change the perceptions of those around them.

So stay tuned here for information on color you can use to improve your gemstone jewelry buying awareness!  Not to mention interest and fun ...

Jennifer

Peridot - Part Four: The Universe Makes Stained Glass Windows

Some of the most beautiful meteorites in the world (and out of the world) belong to the pallasite class of meteorites.  Many pallasites can be recognized immediately by their characteristic crystals of greenish olivine embedded in an iron/nickel matrix.  When these meteorites are cut into thin slices, light can shine through the translucent olivine, creating stunning lattices of metal and gemstone.

The example at left is the meteorite Esquel.  Gorgeous gem quality olvine, known as peridot of course, is liberally strewn through a shiny metal frame.  It seems so perfect, one might think it was manufactured.  But these incredible rocks formed naturally, far away from Earth.

The meteorite Imalac is also a pallasite, with a higher density of olivine to metal, although the olivine is of a more golden hue, and seems less gem-quality.  Some pallasites are almost all metal, while others are predominently olivine.  Each is unique, its own version of a glittering mineral 'window.'  It once was thought that pallasites must come from the interior of an asteroid-like body - the place where the olivine mantle met the iron/nickel core.  But recent studies have indicated that things are not so straightforward.  Pallasites are a glorious mystery.

This gemstone gives us an immediate connection to the heavens.  Something as simply beautiful as peridot is found in abundance in the mantle of the Earth, and is one of the most basic minerals in space rocks, too.  Of course, the Earth is really just a big space rock, itself.

Image Credits: Slice of Esquel meteorite, from flikr via Creative Commons, CC 2.0, Bistrosavage. Closeup of Imilac meteorite, original image from flikr via Creative Commons, CC 2.0, aakova.

The Glories of Amber - Part Three: Types

Amber material as used in jewelry is separated into several types based on processing and genuine amber content. Only the first four categories are recognized by the International Amber Society, but a market exists for all seven categories. And since you’ll encounter all of them when you are looking for amber beads, I list them all here.

1. Natural Baltic Amber is 100% Baltic Amber that has had no treatment that changes natural properties. Allowable changes are mechanical only, such as cutting and polishing. Beads will generally be irregular in shape, from translucent to opaque, come in a variety of colors, and have inclusions and marks. Amber does not naturally weather into round shapes, so round beads are rarely cut from Natural Baltic Amber, since it wastes material. Natural Baltic Amber is very expensive, and while highly desired by some, others are not attracted to the look of amber in this closer to raw state. Must be treated with care.

2. Modified (Heated) Baltic Amber is 100% Baltic Amber that has been subjected to heat, high pressure, or both. This treatment will change the color and clarity of most amber, making it more translucent, and the color more uniform. Beads will still often be irregular, but fewer inclusions and marks will be present. Many larger, quality cabochons are made of Modified Amber. Since these processes greatly improve the look of amber, there is much Modified Amber on the market. It is the alternative to Natural Amber for some, but remains very expensive. Heat treating makes the material somewhat harder and resistant to scratching, but it still must be handled with care.

3. Pressed Amber is 100% Baltic Amber that started out as small pieces. These pieces are then pressed together under high pressure and temperature into a single larger piece. No additional components can be added in this category and have the material still considered 100% Baltic Amber. The pressing process allows for much more uniformity in size, shape, and color. Most round amber beads on the market have been pressed, and are still a pricey choice for their 100% Baltic Amber content. This material is usually a little harder than Modified Amber.

4. Bonded Amber is almost entirely amber, but has a tiny amount of glue or bonding agent added in the process of heating and pressing small pieces together into a larger whole. Usually indistinguishable from Pressed Amber to the naked eye. It can be somewhat less expensive than Pressed Amber, which uses no glues. Similar hardness to Pressed Amber.

5. Ambroid (Amberoid) contains some percentage of genuine Amber or amber chips with another percentage of modern resins. Generally, the higher the percentage of real amber in the material, the higher the quality and cost will be. Quality ambroid, made of a high percentage of genuine Baltic Amber with some added natural modern resins, offers the look of Pressed Amber at a moderate price. However, there is low quality ambroid, made of a small amount of genuine amber and a large amount of synthetic resins, to watch out for. Ambroid is the material that is most often passed of as 100% natural amber in an attempt to get buyers to pay more. Quality Ambroid is a durable material that resists pitting and scratches reasonably well.

6. Copal is not actually amber by any definition, but can resemble amber at a fraction of the price. Copal is much, much younger tree resin that have dried sufficiently that jewelry can be fashioned from it. Price is highly variable, depending on if it is being passed off as “amber.” Untreated copal is still soluble in liquids such as acetone, and so can deteriorate quickly if it comes in contact with certain hair sprays, makeup, and lotions. Must be handled gently.

7. Imitation Amber is also not amber by any definition other than superficial look. This material can be anything, from glass to plastic, that attempts to mimic amber. Usually very inexpensive. If your amber is priced very low, it probably isn’t amber at all. Durability depends entirely on the material.

With all these choices, it can be a little confusing to ensure you are getting exactly what you want at a proper price, but the first step is staying informed! Image Credit:  Amber cabochons, chamberofcommerce.pl

The Glories of Amber - Part Two: Finding and Using

Raw Amber

Gemstones are (for the most part) hidden treasures.  If they are not buried deep underground, then they are in hard to find, off-the-beaten-track places.  This isn't a surprise, since any easy to reach gemstones were found by humans long ago and carted off.  Amber is no exception.

Given that amber is a product of ancient trees, it is now found in the areas where large forests of those trees once existed.  While small amounts might be encountered globally, the largest deposits of amber, possibly 90% of the Earth's retrievable storehouse, can be found on the Baltic Sea.  Baltic amber has long held the position as the most dependable and desirable amber for gemstones (although this market is quite competitive).  Baltic amber is mined, but some amber can actually be found by "fishing."  Since amber is one of the very lightest stones, it will float in saltwater.  Storms in the Baltic Sea stir up the seafloor, and allow nodules of amber to float to the surface.

Cloisonne Necklace Highlighted With
Orange Amber (Ambroid) Beads

Amber burns when heated and gives off a scent like pine.  Because of this, it wasn't only used for jewelry, but for incense and in religious rituals.  Combined with other materials, it was also historically used in perfumes.  Its soft nature allows it to be carved easily, and so it was, and is, used to create pipes, urns, parts of musical instruments, pieces of light fixtures, and much more.  Today the most common use for the best pieces of amber is in high quality jewelry.  Lower quality amber or small pieces are pressed together to create stones that rival the best for beauty, but are considered lesser because they have been through a manufacturing process.  The very lowest quality amber is generally processed into oils and resins.

Finding and using amber is also a trick for the gemstone artist, since this material is expensive, exclusive, and easily imitated.  But more on that later!

Image Credit:
Raw Amber from www.wonderful-denmark.com
Cloisonne Necklace from our site, lunarbluedesigns.etsy.com, one of our unique designs!  This one includes vermeil gold (gold plated over sterling silver) accents, along with Swarovski crystal, amber (ambroid), and fresh water pearl.

The Glories of Amber - Part One: Origins

Amber is a lovely and highly desirable gemstone with a fascinating past.  Each piece has been witness to a metamorphosis from liquid plant matter to prized hardened natural plastic.  Then comes the creation of a chip, bead, or faceted stone, which is then included in a design with its own context and story.

Given the complex history of each nugget of amber, it is no surprise that trying to navigate through the use of amber and amber imitations in jewelry is equally complicated.  Especially since the amber "gemstone" isn't really a stone at all.

Amber begins as a liquid secretion from some trees.  It is not derived from the sap of the tree, but instead comes from the outer layers.  This is a natural hydrocarbon resin, and depending on the source, it can be used in creating lacquers, adhesives, and varnishes.  The use of this substance to the tree is not clear; it might be a way for the tree to rid itself of material it does not need.  Although in some cases it seems that this secretion may either repulse creatures that might eat the tree or attract beneficial insects. 

After secretion, the resin begins to harden, and becomes copal.  Copal can be as little as 1000 years old, and might even be collected right from the surface.  But true amber is an ancient material, tens of millions of years old.  In order to create amber naturally the resin must be buried, perhaps by sediment, and transformed by the high pressures and temperatures underground.  Eventually, enough of the volatile material is driven off that amber is finally formed.  Humans might then find it by searching areas cut into by water and erosion, or mining for it directly.

Depending on the part of the world the amber originates, it is probably 40-50 million years old.  The very oldest amber found *might* be as old as 130-140 million years.  Part of the appeal of this lovely "stone" is the knowledge that it comes from a close genetic relative - trees - and is the product of living processes.

Image Credit:  Insects in Baltic Amber, Wikimedia Commons, CC 3.0
Sterling Post Earrings with Green Amber (Ambroid), Swarovski Crystal, and Malachite - Lunar Blue Designs

Crystal in Handmade Jewelry - Part Three: Crystal Versus Glass - Composition

All Swarovski crystal (in
other words, lead glass)
and sterling silver suncatcher

Having taken a look at Crystal Versus Glass - Structure in my most recent post in the series, let's talk here about chemical composition.

First things first - how is it that a 'wine glass' can be 'crystal'?  Didn't I say previously that crystal had an ordered structure and glass did not?  Yes.  Crystal wine glasses aren't crystal.  They are made of glass.  They are made of a specific kind of glass that has had lead added to it to make it more reflective and prismatic.  The use of 'crystal' to describe this substance is historic, coming from Murano glass manufacturing in Venice.  In those days the manufacturers were trying to imitate some of the properties of natural quartz crystal.  This idiom, or convention, has remained.  'Lead glass' is the same as 'lead crystal' is the same as 'the stuff my crystal wine glass is made of.'

This confusion of terms has translated to the bead market, where both glass, lead glass, and synthetic and natural crystal are all used side by side.

So what is it about high quality, expensive 'crystal', like say Waterford, that makes it so desirable?  Regular water glasses, even if nicely etched and cut, do not have the flash and brilliance of, say, Waterford crystal faceted wine glasses.  As I said before, lead has been added to regular 'glass' to make it 'lead crystal'.  Lead increases the index of refraction of regular glass, which means that light going through the material is reflected around more, and also split like a prism.  'Fine cut lead crystal' is a phrase that means a sparkling, fiery wine glass that will look impressive on the dinner table.

Gorgeous trio of designer glass
earrings.  Even the Swarovski crystal
accents are of course glass.

The same is true for beads.  Beads made of standard glass will not have the same flash and brilliance as lead crystal, even if they are the exact same color and cut in the same way.  This does not mean that 'glass' is bad.  Not at all.  Remember, these kinds of 'crystal' beads are in fact glass.  This is simply glass with lead added to it make it sparkly.  Glass is a fantastic substance that makes highly desirable and sought after jewelry.  I adore glass, and am a huge fan of Murano beads, designer lampwork, and glittering dichroic creations.  The point is to know what you are using in your work as a designer, and what you are buying as a consumer.

I'll talk more about why I choose to use various glass and crystal materials in a later post!

Images:  Suncatcher and earrings are our designs, and available in our Etsy store.  Stop by to see these and similar items!

Crystal In Handmade Jewelry - Part Two: Crystal versus Glass Structure

Our 11" Suncatcher Talisman showing
off a variety of crystalline solids, such
as a smoky quartz faceted crystal
teardrop.

In Part One of my series of posts on 'crystal' I talked about many of the different definitions and uses for this common word in handmade jewelry business.  As this series continues, I am going to focus on each of the various views of 'crystal' and hopefully dispel some of the ambiguity.

A common place to find confusion is in the use of 'crystal' versus 'glass' in the materials listed for a handmade piece.  To a geologist, these terms have a specific difference based on structure.  To a bead artist, these terms are more likely to be differentiated based on chemical content.  Let's talk about structure first ...

'Glass' is a solid substance where the structure of the atoms is irregular and amorphous (and which will turn into a liquid when enough heat is applied).  There is no large scale order to be found in 'glass'.  Conversely, the structure of a 'crystalline' solid is very regular.  The internal matrix of a crystal is repetitive and highly ordered.

It is possible to have a 'glassy' form of a material that has the exact chemical composition as a 'crystalline' form.  The most most well known crystal is quartz, made of silicon and oxygen, SiO2, in a nice repeating pattern.  But SiO2 is also the major constituent of 90% of the glass in our everyday lives.  A crystalline substance can be formed by cooling a liquid slowly, allowing the atoms to line up into a nice, repeating pattern as the stuff becomes solid.  A glassy substance can be formed by cooling a liquid very quickly.  The stuff becomes a solid before the atoms have time to line up.

This means that any 'crystal' in a necklace need only be made of a solid with a repeating structure to be referred to as 'crystal'.  A designer that uses quartz crystal in a necklace will call it crystal, and be absolutely correct.  Yet this can be misleading if you imagine all crystal means 'Swarovski.'

I'll post soon about crystal versus glass - composition!

Jennifer

Crystal in Handmade Jewelry - Part One: More Than One Definition

Quartz crystal point in back, propping
up a rhyolite gemstone flecked with
crystal inclusions

Hello Gemstone Fans:

'Crystal' is a common constituent of handmade jewelry, but the word is very often used in ways that are confusing.  Is the designer talking about the composition of the material, its shape, its clarity, or saying it is a single piece of rock, uncut?  When designers describe their jewelry, sometimes they do not provide enough information to let the buyer know exactly what they are getting.  Unscrupulous sellers may even allow misinterpretations to remain unaddressed, hoping the buyer will think they are getting something of higher quality than what is actually included in the piece.

So to start, I simply want to point out how problematic the word 'crystal' can be.  In the first image above, we see a nicely formed quartz crystal.  Some people would call it a crystal because of the regular geometric shape.  Others might think 'crystal' because it is made of solid quartz.   A geologist might call it a crystal because it is a uncut chunk of a mineral in its natural form, or because its atoms are in a nicely regular matrix, instead of scattered about amorphously.  A geologist would also use the word 'crystals' to describe the granules of different minerals found in the rhyolite.

Crystal martini glass displays a pair
of earrings, each with a crystal
bicone bead on top.

More examples of 'crystal' are in the second image.  For some, the only crystal they are familiar with on a daily basis are cut crystal glasses and bowls used for dining or serving.  For others, the word crystal always means bright, sparkly, glassy looking beads, like those found atop the shells in this pair of earrings.  It may be that the chemical content of the beads isn't at all what they are thinking of, simply their common shapes, colors, and flash.

So with all the different ideas for what a 'crystal' is, or what 'crystal' can mean, there is no surprise that confusion exists.  Stay tuned here for more information about how you can be more informed about what is in your jewelry, and how to make sure you are getting exactly what you want!

Jennifer

Peridot - Part 3: Weathering With Time

Hello Gemstone Fans:

I started this series of posts by saying that olivine was hardly a rare stone, what with it making up a substantial portion of the Earth's interior. And then, of course, I turned that on its head by saying that while olivine under the surface is common, olivine on the surface is hard to find. It is especially hard to find in the quality peridot needed to make cut gemstones, in fact.

The first reason such material is rare is that in order to get it to the surface, you need volcanism with magmas of the right composition, as I mentioned in my second post. The second reason is that olivine is not a particularly hard stone, and what peridot makes it to the surface weathers quickly. Weathering can take the form of physical weathering, which grinds down stones over time into small particles, and it can take the form of chemical weathering, where say water interacts with the stones and breaks down their crystalline structure.

On the Mohs hardness scale, peridot measures 6.5 to 7 (Diamond is the hardest at 10, with emeralds and sapphires at 9. Soft materials have low numbers, like talc at 1 and amber at 2.)  This means there are many harder materials in the environment that can scratch peridot, assisting in its break down.

But this phenomenon does have some interesting effects. There are places on Earth where you can find stretches of sparkling green sand. Hawaii is one of these places, where there are small beaches of sand largely composed of grains of olivine.

How do such concentrations of olivine grains come to be? Hawaii is, of course, a volcanic island, with active volcanism today. There are places on the island where the black rocks are rich in olivine crystals. As those rocks weather and break down, the crystals of olivine trapped inside are liberated, and moved by wind and rain downslope. A green sand beach may form in any area where the nearby rocks are rich in olivine, and where the shape of the coastline can protect the sand.  That way it collects there at approximately the same rate it is broken down or washed away. 

I have traveled to the most well known of these beaches (shown in the top image) the green sand beach near South Point in Hawaii. There are other beaches with sands of interesting color, such as black, pink, white, and red. But on this beach I got to walk barefoot on piles of tiny, glittering green gemstones. I felt a little like a dragon with a hoard of gems ...

Jennifer

Image Credist: 
Green Sand Beach, South Point Hawaii, Wikimedia Commons, CC 2.0
Green Sand Closeup from Mahuna Beach, Wikimedia Commons, Public Domain

Peridot - Part 2: From the Depths to the Surface

Greetings Gemstone Fans:

I mentioned in my post Peridot - Part 1 that the mineral olivine, known in gem-quality as peridot, can be brought up from depth by volcanism.  I visited one of these sites in New Mexico - Kilbourne Hole, a volcanic explosion crater - and got to see the results for myself.

Such craters are called "maar" craters, and are made by a shallow underground volcanic explosion. They were once confused with impact craters, which are caused by chunks of rock or metal from space striking the planet's surface. In fact, the craters on the Moon were thought by many to have been caused by volcanism, and were only shown to certainly be of impact origin after we visited there in person.

Kilbourne Hole is off the beaten path in southern New Mexico, but not so remote that it can't be found by dedicated stone hunters. (As it happens, I do not visit sites to hunt rocks, I visit them as a geoscientist, and was there to learn about the geology.) This maar is found on federal BLM land, not a national or state park, so is not protected in the same way. Larger crystals of olivine have long since been carried off by rock hounds, but there are patches of sand-sized green crystals remaining. Many of these were produced by rock hunters shattering thousands of olivine xenoliths looking for gem quality stones. There are only a handful of places on the Earth where olivine crystals are found on the surface like this, and so such sites are very popular.

Rarely at this site, one might find a volcanic rock, dark basalt, with splashes or crystals of bright green glassy material still clinging to it. The picture here shows just such a rock, encrusted with forsterite crystals. Forsterite is the name for olivine crystals that have a lot of magnesium in them, as opposed to fayalite, which is the more iron-rich end of the olivine spectrum. Such chemical differences are important to geologists who are trying to understand the volcanic history of the area.

It really is an amazing thought to look at this material and ponder how deeply in the planet it may have started its journey before making it to the surface. Not to mention the dramatic way it finally arrived.

Jennifer

Image Credits:

Kilbourne Hole - Bureau of Land Management, www.blm.com

Forsterite Crystals from Kilbourne Hole - Wikimedia Commons, Rob Lavinsky, iRocks.com – CC-BY-SA-3.0

Peridot - Part 1: Gem of the Earth's Interior

Greetings Gemstone Fans:

I thought I'd open up my blogging about beading materials with a series of posts on the gemstone peridot. This is the lovely green stone commonly known as August's birthstone. In gem-quality, it is peridot, but the mineral is known to geologists as olivine. The basic part of its structure is created by silicon and oxygen, as with most other 'rocky' minerals on Earth. Olivine also contains varying amounts of magnesium and iron.

We imagine that a gemstone held as precious by humans must be quite an oddity - something very rare. Yet olivine in its many forms is one of the most abundant minerals making up the planet Earth.

In fact, olivine accounts for the bulk of the Earth's upper mantle. The mantle is that thick, voluminous layer that sits between the Earth's thin crust and its core of iron and nickel. In this image, the mantle is (appropriately) green, with the upper mantle labeled as region three.

Because of the important role olivine plays in the Earth's composition, and its place in the upper mantle, geologists spend a great deal of time trying to understand how the mineral behaves at different pressures and temperatures, and which forms are created when and where. This information is needed to properly model heat flow, as well as the movement of the continental plates. So this stone is not only of interest to gem fans, it is a critical piece of Earth's geologic puzzle.

When you touch peridot, it is like touching the inside of the planet. Or possibly literally touching it, since some peridot is brought up to the surface from the depths by volcanism.

Jennifer







Image Credits:
Large Peridot Gem - From Picasa Web Albums, AfricaGems, via Creative Commons
Earth's Interior Layers - Wikimedia, via Creative Commons
Green Quartz and Peridot Necklace - Lunar Blue Designs, Amy's Personal Collection