What are gemstone inclusions?

Inclusions are solids, liquids, or gases that became trapped in a gem while it was forming.  A gemstone may contain more than one type of inclusion. 

Aren’t inclusions bad?

While it’s true that visible inclusions decrease the beauty and value of many types of gemstones (diamonds being the best known example), some gemstones with inclusions are quite desirable.  Some gemstones wouldn’t even exist if it weren’t for inclusions. 

In addition, inclusions provide important information to gemologists.  Some inclusions are only found in specific gems and others help differentiate natural and synthetic (man-made) gemstones.   Inclusions can provide information on what region or even what mine a gem came from. 

What gems with inclusions are desirable?

There are many types of included gems, but only a relatively small number are considered beautiful and tough enough for jewelry and are widely available.  I’m going to give examples in 2 categories: inclusions that are the main attraction and phenomena caused by inclusions.

Inclusions as the Main Attraction

 Amber, which is fossilized tree sap, may have inclusions of plants or animals.  Amber with good quality inclusions can command very high prices.

Quartz is one of the most common host gems for inclusions, likely because it is one of the last minerals to crystallize during the cooling of molten material. 

Rutilated quartz: Rutile’s needle-like crystals are commonly gold, black, or red.  Rutile inclusions may occur as a few individual needles, throughout a stone, or in clusters.  Occasionally golden rutile radiates out from a central hematite inclusion in a very desirable star pattern.

Tourmalinated quartz: While tourmaline comes in a rainbow of colors, tourmalinated quartz used in jewelry usually contains black crystals and can look similar to rutilated quartz.  The cross section of a tourmaline crystal intersecting the surface of the quartz may show a characteristic modified triangular or hexagonal shape. 

Phenomena Caused by Inclusions

Several of the phenomena seen in gemstones are caused by inclusions that may be invisible or barely visible to the naked eye.  Some phenomena such as asterism and cat’s eyes require the gem be cut as a cabochon and properly oriented to show off the effect.

Asterism is the name for the 4, 6, or 12 rayed star effects seen in gems including sapphire, ruby, diopside, quartz, and others.  It is caused when needle-like inclusions, commonly of the mineral rutile, but also ilmenite or magnetite, crystallize in orientations that create the star.

Chatoyancy is the silky sheen or band of light seen when light shines on parallel bundles of needle-like or fibrous minerals or hollow tube inclusions within the gem.  The “cat’s eye” effect is a type of chatoyancy.  Some common chatoyant gems are chrysoberyl and tiger’s eye.  Other gems including beryl and tourmaline may show chatoyancy when the right inclusions oriented correctly are present.

Aventurescence (sometimes called Schiller effect) is caused by small flat inclusions that reflect light.  Common gems with aventurescence include aventurine (containing fuschite, a green mica), and sunstone (copper, hematite, and/or ilmenite). 

Learn more about phenomena in gemstones here.

Inclusion Conclusion

There are many other beautiful and unique gems with inclusions.  I’ve only highlighted some of the more common varieties here, but I hope you have a new appreciation of the beauty that can be contained within a gem!

Resources & Additional Reading:

https://www.gemsociety.org/article/inclusions/

https://www.bwsmigel.info/geol-115-essays/gemology-included-quartz.html

http://www.quartzpage.de/inc_text.html

https://www.gia.edu/amber

https://www.gems-inclusions.com/

Have you stopped wearing a favorite piece of jewelry because the stones look dull or the metal is no longer shiny? A simple cleaning may be enough to make it sparkle again!

The photo shows the results of a quick dip in silver cleaner for some of my earrings (I don’t always keep up with my jewelry cleaning either!).

There are many options for cleaning jewelry, but not all methods are appropriate for all types of gems or metals. Heat, vibration, or chemicals can damage many types of gemstones. At the end of this post I’ve provided links to articles that can help you choose the best cleaning method for common gemstones.

Here are some common jewelry cleaning methods:

Dish Soap & Warm Water: This method is fine for virtually all gems (pearls need special care). Simply soak the jewelry in warm (not hot) water with a few drops of mild dish soap. Use a soft brush (I use a soft toothbrush) to remove dirt, paying attention to the backs and sides of settings, clasps, and between set stones or beads. Rinse with clean warm water and dry with a soft cloth. If you are cleaning your jewelry in a sink, be sure to close or block the drain first! This method will not remove tarnish from silver.

Liquid Jewelry Cleaners: There are any number of brands of liquid jewelry cleaners available but I don’t find that they work better than dish soap and warm water. However, they often come with handy strainers for dipping your jewelry into the cleaner and soft brushes for getting into crevices.

Polishing Cloths: There are many types available; some are impregnated with polishing compounds and are particularly useful for cleaning metals. There are also special cloths for cleaning gemstones (without any abrasives). I am personally fond of the Sunshine brand of polishing cloths and find them particularly useful for cleaning bezel settings, clasps and extender chains, and metal beads next to soft gemstones.

Silver Dips: Silver dips are a fast and easy way to remove tarnish (and what I used to clean the earrings shown in the picture above). They are great for getting into places that can be hard to reach with a cloth. These cleaners are not safe for use with soft stones (I’ve ruined both malachite and lapis lazuli in the past). Read any instructions carefully and check the resources below to see if chemical cleaners are safe for your jewelry. Be sure to rinse and dry jewelry thoroughly after using a chemical dip.

Jewelry Polishes: There are many types of polishes on the market including some specifically for sterling silver, and some with a wider range of applications. I have had very good luck using the Jewel Brite brand which cleans metals, removes tarnish from silver, and is safe for all gemstones. Always use soft cloths (not paper towels), and rinse and dry thoroughly. Read and follow the manufacturers directions carefully.

Ultrasonic Cleaners: Ultrasonic cleaners use high frequency sound waves that create tiny microscopic bubbles that actually implode (the action is called cavitation). This action loosens the dirt and oil on your jewelry. Ultrasonic cleaners come in sizes for both home and professional use. A cleaning solution is added to the water in the cleaner (you can buy specialty cleaners or just use mild dish soap). Professional models may include a water heater while most personal use machines do not. Be sure to check if your stone can handle the vibrations from an ultrasonic cleaner at one of the sources listed below. If you’re not sure, don’t do it. This method will not remove silver tarnish.

Steam Cleaners: These cleaners use blasts of high pressure steam to remove dirt and oils from jewelry. Steam cleaners are mostly used by jewelry professionals rather than consumers. They are very quick and effective but many gemstones are too delicate to be cleaned by this method.

Some other considerations:
* Whatever method you use, always be sure your jewelry is dry before placing it back into your jewelry box.
* With any of these methods, if you’re not sure if it will damage your jewelry, either don’t do it or find a spot that won’t be seen to test before cleaning the entire piece.
* Some jewelry may have been purposefully “blackened” to highlight a recessed design or for other artistic reasons. These items should be hand cleaned carefully so as not to remove the blackening agent.
* It is a good idea to examine your jewelry for loose or damaged stones or settings before using ultrasonic or steam cleaners. The force of the steam or vibrations from the ultrasonic can occasionally knock stones out of their settings.
* Fine gemstone jewelry should be taken to a jeweler once a year to have settings, such as prongs, inspected for damage or wear. Some jewelry stores may offer complementary jewelry cleaning for their customers.
* For jewelry you no longer enjoy wearing, please read my blog “8 Ways to Clean Out Jewelry Clutter“.

Jewelry and gemstone cleaning and care links:

The Gemological Society of America (GIA) has lots of information on care of gemstones. I really like their Gem Cleaning and Display Chart which you can download for free and includes information on heat and sunlight sensitivity of gems. Here’s a more general article titled “Tips on Caring for Jewelry“.

Here’s a Gemstone Cleaning Chart from Fire Mountain Gems.

Before I tell you about my road trip, let me answer the most common question I hear about peridot: is it pronounced per-ə-ˌdät or per-ə-dō(t)?!  As my father would say, the answer is “yes”.  Both pronunciations are correct.

I recently took a road trip to the town of Peridot, Arizona (locally pronounced per-ə-ˌdät).  Peridot Mesa is the premier location for mining the gem in the United States.

Location map

Happy geologist!

The peridot mine is located on the San Carlos Apache Indian Reservation.  Collecting in this area is very strictly regulated; you must obtain a permit and even then you can only access the area when guided by a claim holder.  Once at the mine, you must remain on the claim owned by your guide.  I was able to visit the mine with Stevie Joey, who has been mining his family’s claim for many years.  Most of the work is done using a jack hammer, but larger equipment is brought in to move overburden material and open new locations.

Me (l), Stevie Joey (r)

Peridotite at the mine site

The peridot crystals are found in peridotite xenoliths (say that 10 times fast).  Xenoliths are pieces of preexisting rock that are ripped out of place as molten magma moves through the depths of the earth.  The earth’s upper mantle consists of peridotite, a rock composed of olivine as well as several other minerals.  The magma picked up pieces of peridotite and carried them to the surface.  The heat of the magma started to melt the rocks resulting in the rounded edges of the inclusions (see photo below left).  Olivine is the green mineral in peridotite and when it’s found in gem quality (good color and clarity), it is known as the gem peridot.  The peridotite at the mine is very crumbly which is why there’s so much green sand around.  The rock surrounding the peridotite xenoliths is basalt – the rock that forms when lava cools.  So what we’re seeing here was part of the earth’s mantle – pretty darn amazing!

Xenoliths

Large olivene crystal

Most of the pieces of peridot I found were very small, but larger pieces can be found.  I tried to remove the large dark crystal in the photo above right, but it was internally fractured and didn’t make it out in one piece.  I came home with a few nice samples of peridotite, but no large pieces of peridot.  An opportunity to see one of the world’s most interesting source of gems was an adventure worth having!

References & Resources:

Pronunciation:
https://www.merriam-webster.com/dictionary/peridot

About the area:
https://www.youtube.com/watch?v=6Pp2rydb8cI
https://en.wikipedia.org/wiki/Peridot_Mesa
To visit, contact Stevie Joey: http://www.peridotdreams.com/

Peridot and peridotite:
https://mochisgifts.com/2015/08/02/peridot/
https://minerals.usgs.gov/minerals/pubs/commodity/gemstones/sp14-95/peridot.html
https://www.gia.edu/peridot
https://www.mindat.org/min-48407.html
https://en.wikipedia.org/wiki/Peridotite

Photos (c) 2018, J. Fenton

Polymorphism is one of the many fascinating properties of some minerals.  Polymorphs are minerals with the same chemical formula but different internal arrangement of  molecules.  This results in different external crystal shapes (called “habits”).    The resulting mineral depends mostly on the combination of temperature and pressure that were present at the time of formation.  A polymorph pair that may be familiar to you is diamond and graphite.  Both are composed of a single element, carbon (C), but crystallize very differently as shown below.

This example shows you how very different polymorphs can be, both in how they look and in their physical properties; graphite has a hardness of 1-2 on the Moh’s Scale while diamond is 10.  Another polymorphic gemstone that I use in  jewelry is kyanite (Al₂SiO₅): both andalusite and sillimanite are  polymorphs.

Marcasite and pyrite are also polymorphs with the chemical formula FeS₂  (iron sulfide).  Both have a hardness of 6-6 1/2, however marcasite crystallizes in the orthorhombic system while pyrite is isometric. In addition, marcasite crystals are not very stable so it turns out that marcasite jewelry is almost always made from pyrite.  I guess the name “marcasite” sells more jewelry than “pyrite”!

Natural pyrite cubes and assorted pyrite beads from my collection.

Pyrite is one of the best known minerals – almost every child has a piece in their rock collection.  Pyrite crystals can occur as near perfect cubes, or as pyritohedrons.  Pyrite is often called “fool’s gold” for it’s bright brassy color and metallic luster.  Next to real gold, the difference is obvious, but if you’re out mineral hunting and a piece of pyrite sparkles in the sun, it’s easy to be confused. As mentioned above, pyrite has a hardness of 6-6 1/2 while pure gold is only 2.5. Pyrite is an iron mineral so it is relatively heavy.

Lapis lazuli is a rock composed of three minerals, lazurite, pyrite, and calcite.   I enjoy using pyrite as an accent to bring out the pyrite included in lapis lazuli (and it looks great with azurite and other gems too).

Pyrite should not be cleaned with water; clean it with a soft cloth. Over time, pyrite may tarnish or dull and can leave black residue, so you may not want to wear it over light colored fabrics.

Now you won’t be a fool when choosing jewelry with pyrite!

References:
https://www.gemselect.com/other-info/marcasite-pyrite.php
https://www.mindat.org/min-2571.html
https://www.mindat.org/min-3314.html

Malachite has always been one of my favorite gemstones for jewelry so I’m not sure what took me so long to get around to telling you about it!

Malachite necklace on malachite specimen with silky texture.

Malachite is a relatively common mineral associated with oxidized copper veins. It has the chemical formula Cu₂(CO₃)(OH)₂. Malachite is easily recognized by the beautiful color banding of shades of bluish-green to darker green and almost black. Mineral specimens can be found showing many different habits; commonly botryoidal (rounded grape-like masses) with fibrous or silky structure, small crystals, stalactites, and tufts.

Azurmalachite pendant.

Although malachite can be a minor ore of copper, it is mostly used for jewelry and carvings. It is commonly found in combination with other minerals; for jewelry use, azurite (azurmalachite), chrysocolla, and shattuckite often show up in the mix.

 Historically, large quantities of malachite came from Russia, but this supply has been mostly exhausted. Currently, malachite is mined in Australia, Chile, the Democratic Republic of Congo, France, Namibia, the United States (Arizona), and Zimbabwe.

Knowledge of malachite goes as far back as the ancient Egyptians, Greeks, and Romans where it was used for jewelry, eye shadow, and as a pigment for paints. Paint using malachite has been found in Egyptian tombs and in European paintings from the 15th and 16th centuries. A stunning use of malachite can be seen at the Winter Palace at the Hermitage Museum in St. Petersburg, Russia,  which features “the Malachite Room” with  ornamental columns, vases and fireplace panels made from malachite.

There are both synthetic and imitation versions of malachite. With a little practice, they can be easily recognized.

Malachite is very soft (3.5 – 4 on the Moh’s Scale of Mineral Hardness) and scratches easily. It is also sensitive to chemicals and is sometimes coated with resin or wax to help protect it. Malachite necklaces and earrings are less likely to incur damage than rings or bracelets. Malachite jewelry should be cleaned with mild dish soap and water and a soft brush. Do not use steamers or chemical or ultrasonic cleaners as they can damage the stone and/or remove any protective coatings.

Malachite earrings.

Every piece of malachite is unique and a wonderful addition to your jewelry collection!

References:
https://www.mindat.org/min-2550.html
https://www.gemselect.com/gem-info/malachite/malachite-info.php
https://geology.com/minerals/malachite.shtml
Hurlbut, Cornelius S.; Klein, Cornelis, 1985, Manual of Mineralogy, 20th ed., John Wiley and Sons, New York.

Today I’m going to discuss the similarities and differences between labradorite, moonstone, and rainbow moonstone. I’ve noticed that most customers who ask for moonstone jewelry really mean rainbow moonstone, they just don’t know it!

All three of these gems are part of the feldspar group of silicate minerals that have a hardness of 6 – 6 1/2 on the Moh’s scale. Feldspar is a very common rock forming mineral, but it has a range of chemical composition leading to many different varieties of minerals in this group.  Within the chemical formula of feldspar, several different elements can be substituted in part or completely by another element. Only a few of the many different feldspar minerals are rare or beautiful enough to be considered gems.

All three gems show “phenomena”; special optical effects due to how they transmit and reflect light.  Read more about the different phenomena mentioned below in these blog posts: Part 1, Part 2.

Labradorite:

Labradorite pendant and beads showing labradorescence

Labradorite is classified as a plagioclase feldspar with the chemical formula (Ca,Na)[Al(Al,Si)Si₂O₈]. This formula shows that there can be some variation in the relative proportions of calcium and sodium, and aluminum and silica, and still be classified as labradorite.

Labradorite was named for where it was discovered, Labrador, Canada. What makes this gem special is the phenomenon of “labradorescence” (great originality in naming). Without direct light, the gem generally appears gray. In the light, vibrant blues and greens flash across the surface. Sometimes gold, pink, or other colors are also seen; the name “spectrolite” is sometimes used in this case.

Moonstone:
Moonstone is the gem form of the mineral orthoclase (potassium feldspar, sometimes

Some of the colors of moonstone.

called K-spar) with the chemical formula ‎KAlSi₃O_8.  

Common colors include white, gray, and orange. Less commonly seen are yellow or brown. Moonstone’s phenomenon is called “adularescence” which gives the gems a whitish sheen or cloud that appears to float within the stone. This sheen, which appears to some to look like the moon shimmering in the sky, is the source of the name.

Rainbow Moonstone:

Rainbow moonstone (labradorite).

Here’s the chemical formula for rainbow moonstone: (Ca,Na)[Al(Al,Si)Si₂O₈]. It’s exactly the same as labradorite because … rainbow moonstone is actually a variety of labradorite!

Rainbow moonstone can be transparent to translucent white. Rainbow moonstone also shows adularescence, but the sheen is blue, sometimes with other colors, and is caused by the same mineral structure that causes labradorescence.

All three gems are feldspars and all are beautiful – their differences are just a matter of chemistry. My favorite of the three is labradorite. What’s yours?

References
GIA Gem Identification Lab Manual, May 2012.
Hurlbut, Cornelius S.; Klein, Cornelis, 1985, Manual of Mineralogy, 20th ed., John Wiley and Sons, New York.
https://www.mindat.org
https://www.gemdat.org
https://www.gemselect.com

All photos © J. Fenton, Mochi’s Gifts, 2018

Topaz is one of November’s birthstones (citrine is the other), but it is not as well known as many other birthstones. This may possibly be because many people think of drab yellow or brown hues when they think of topaz. I hope to remedy that misconception here, not least of all because it’s MY birthstone!

GENERAL INFORMATION:
Topaz has the chemical formula Al₂(F,OH)₂SiO₄ and grows in long prismatic crystals. Well formed crystals often show a characteristic “chisel point”.  Although topaz is one of the hardest gemstones at 8 on the Moh’s Scale of Mineral Hardness, it is not very tough and is susceptible to breakage from impact or temperature changes. It’s best used in earrings and necklaces and should be worn in protective settings such as bezels when used for rings.

Topaz is found in many countries including the United States, China, India, Myanmar, Russia, Sri Lanka, and Vietnam.  Commercial mining areas include Brazil, Madagascar, Namibia, and Pakistan.

Topaz crystal from Utah showing “chisel point” termination.  Photo (c) J. Fenton, 2017

COLOR:
Besides yellow and brown, topaz occurs naturally in orange, pink, purple, red, light blue and light green as well as colorless crystals.  Orangey-red to pink gems may be called Imperial Topaz and are among the most valuable colors.

Sapphire and blue topaz necklace. Photo (c) J. Fenton, 2017

TREATMENTS:
Blue topaz: Prior to researching this article, I was unaware of naturally occurring blue topaz. It’s quite rare and most blue topaz found in jewelry comes from colorless material that has been irradiated and heated.  There are several methods of treatment; for more information read this article.  The combination of heat and irradiation results in a range of blue colors; “Swiss blue” and “London blue” are two common trade names.  The treatment is stable and permanent.

Mystic topaz: Colorless topaz is enhanced with a thin covering of an iridescent film.  This gives the gem a beautiful display of different colors as you move it in the light. The treatment is not permanent; the film can be scratched or polished off.  Care should be taken to avoid abrasion to the surface when wearing this gem.

CARE:
Clean your topaz jewelry in warm soapy water; don’t use steamers or ultrasonic cleaners.

References:
https://www.gia.edu/topaz
http://4cs.gia.edu/en-us/blog/november-birthstone-topaz-and-citrine/
https://www.gemselect.com/gem-info/mystic-topaz/mystic-topaz-info.php
https://en.wikipedia.org/wiki/Mohs_scale_of_mineral_hardness
Hurlbut, Cornelius S.; Klein, Cornelis, 1985, Manual of Mineralogy, 20th ed., John Wiley and Sons, New York.

Pure beryl (Be₃Al₂Si₆O₁₈) is colorless and is known as “goshenite“.  Beryl is a gem species; the addition of trace elements can result in one of its many varieties including:

Emerald – May’s birthstone is colored by chromium or vanadium and is the most valuable of the beryls.  Emeralds are medium to dark bluish-green to yellowish-green.  Light colored gems are referred to simply as “green beryl“.  Emeralds commonly have many inclusions and fractures so large gems are uncommon.  Most commercially mined emeralds come from Colombia, Zambia, Brazil, and Zimbabwe.  Emeralds can be found in the United States in North Carolina.

Emerald crystals (Photo: public domain)

Aquamarine – March’s birthstone gets its blue color from iron.  Aquamarines are light blue-green; medium to dark blue gems are known as “maxixe beryl“.   Large clean aquamarine gems are common.  Aquamarine is mined in Brazil, Nigeria, Zambia, Mozambique, Madagascar, Pakistan, and Vietnam.  In the United States, aquamarine can be found in Colorado, Idaho, and Wyoming.

Aquamarine, rainbow moonstone and amethyst necklace (Photo: J. Fenton 2017)

Morganite -Manganese gives morganite its pink to peach color.  This lesser known beryl has been gaining in popularity in recent years.  It was discovered in 1910 in Madagascar and was named for the financier J.P. Morgan.  The gem is also found in Brazil, Afghanistan and Mozambique.  Morganite has been found in California and Maine in the United States.

Heliodor (also Golden or Yellow Beryl) – Heliodor is generally considered a collectors gemstone and is not often found in jewelry.  Traces of iron cause the greenish-yellow to orangy-yellow color.

Red Beryl (Bixbite) – Red beryl is quite rare and has been found only relatively small crystal sizes.  Manganese provides the red color which is very saturated in this gem.  It is  found in the United States in Utah and small crystals have also been found in New Mexico.

Of the varieties above, I’ve seen beads made from emerald, aquamarine, morganite, and green beryl.  So now you know beryl!

References:
https://www.gia.edu/gia-gem-project-beryl
https://www.gia.edu/gem-encyclopedia
http://geology.com/minerals/beryl.shtml
GIA Gem Identification Lab Manual, May 2012
https://en.wikipedia.org/wiki/Beryl