About The Stones F - M

Posted by Elisabeth Dignan on

GARNET The name garnet actually refers to a group of closely related minerals, rather than a single mineral. There are many varieties within two subtypes. Most people think of garnet as red, but in fact, it comes in almost any color. Garnet has been loved for millennia, notably Egyptian pharaohs would wear garnet necklaces that were later entombed with them. Garnet makes a wonderful gemstone but also has industrial uses. It can sometimes display asterism – a star-like light refraction. Garnet is the birthstone for January. It is not typically treated in any way. 

  • ALMANDINE The most common member of the garnet group. Most almandine is opaque, rough, and not gemstone quality, but there are still more faceted stones cut from almandine than any other variety of garnet. 
  • GROSSULAR Grossular garnet is a variety of garnet with the most variation in color within its group. The colors are created by impurities, as pure grossular is colorless. Rare green tsavorite is the most valuable in the grossular variety, but hessonite is important as well. Using the term “grossular” alone refers to the yellowish to yellowish-green color of stone.
  • TSAVORITE Tsavorite (which may sometimes be called tsavolite), despite its’ vibrant green hue, is actually a variety of garnet, in the grossular group! Specifically, the grossular garnet group. It was discovered in 1967 in Tanzania. It has a slightly sordid history, with one of the early prospectors being murdered over access to and control over mines. Aside from Tanzania, tsavorite has be found in Madagascar, Pakistan, and Antarctica. 
  • HESSONITE Reddish-orange variety of grossular garnet.
  • PYROPE An individual member of the garnet group, deep blood red in hue. It is rarer than its almandine counterpart. It often has excellent transparency and is free from flaws.
    • RHODOLITE Raspberry red garnet, composed of a mix of pyrope and almandine. Usually contains more magnesium than iron, making it closer to pyrope. 
  • SPESSARITE An individual member of the garnet group, spessartite is an orange to reddish-brown garnet. “Spessartite garnet” is used in the gem trade, while the term “spessartine garnet” is used more often in the mineral trade. The most desirable hue is fiery red with an orange tint.

 

GREEN ONYX Most of the beads and stones called “green onyx” are actually dyed green chalcedony. The term may also be used to describe white and green banded agate. To the best of my knowledge, the mineral onyx in a green color is never actually used for beads or jewelry. The hue of green tends to lean towards blue-green and it is often semi-translucent. It is status quo to refer to dyed green chalcedony as green onyx.

 

HERKIMER DIAMOND Herkimer diamonds are not diamonds at all, rather they are double terminated quartz. They are colorless to smoky with a wide range of inclusions. They come from Herkimer County, New York – these are the only ones that should be called Herkimer diamonds. Other double terminated quartz comes from Pakistan and may be referred to as “Perkimer diamonds” or “Pakinstan Herkimer.” It should be noted by the salesperson that these stones are not from Herkimer County. No matter where its origin, this stone is truly unique and is stunning in its natural form, without being cut. Herkimer diamonds are not treated.

 

IOLITE Iolite’s name comes from the Greek “ios,” meaning water. It was once called water sapphire. Iolite can pelochroism – it may look different hues from different angles. Iolite is not commonly treated.

 

JASPER Jasper is an opaque variety of chalcedony – just like agate, except that agate is transluscent or semitransparent. Chalcedony is a variety of quartz. The name comes from several languages and means “spotted or specked stone.” Jasper comes in many, many patterns and colors / color combinations. Occasionally it is dyed. Heliotrope (“bloodstone”) is a well-known, popular variety of jasper.

 

  • PICASSO JASPER Named after painter Pablo Picasso, Picasso Jasper is also known as Picasso Stone. Information about this particular stone, which features beautiful patterning and colors, is somewhat elusive. I’ve had trouble finding out much about it, other than it seems to actually be a metamorphic limestone - dolomite (marble), not jasper after all. Thus, the more correct name for it is Picasso Stone, although most people continue to use the misnomer Jasper. It is mined in the state of Utah, United States.

 

  • BLACK JASPER The black and flinty version of jasper is a rarer form. It is occasionally called Basanite or Blackstone.

 

  • EXOTICA / SCI-FI / PORCELAIN JASPER This variety of jasper may be called exotica, sci-fi, or porcelain. All of the names make sense when you see the colors and patterns! It has pink, mauve, beige, cream, and even some purple, and can have dark veining. It is mined primarily in Mexico and was treasured by the ancient Maya elite, as it was a mark of nobility to possess this stone. They believed it had magical powers. Jasper is an opaque variety of chalcedony – just like agate, except that agate is transluscent or semitransparent. Chalcedony is a variety of quartz. The name comes from several languages and means “spotted or specked stone.”

 

  • BUMBLEBEE JASPER So named for its bright yellow color, streaked with black, bumblebee jasper is not jasper at all. It is a combination of many minerals, but contains no quartz that would make it qualify as jasper. It is born from an environment of volcanic ash and sediment. It is found at Mount Papandayan, West Java, Indonesia.

 

  • AFRICAN TURQUOISE Not turquoise at all, African “turquoise” is actually a type of jasper found in Africa. It is typically dyed to achieve the color that looks like traditional turquoise. The natural matrix is what helps it mimic turquoise so well. African turquoise jasper is harder on the Mohs scale than turquoise, making it a good substitute when the customer wants a less fragile, more affordable option. This stone is often sold simply as “African turquoise” which is a misleading misnomer and it should always be clarified that this stone is jasper.

 

KUNZITE Kunzite ranges from soft pastel pink to vibrant violet purple. A newer gem, it was first recognized in 1902 and named after the famed gemologist George Frederick Kunz, who identified it as a unique variety of the mineral spodumene. The color of kunzite comes from trace amounts of manganese. Kunzite can be irradiated or heat-treated to enhance its color. Exposure to heat or bright light can fade the color of natural or treated kunzite.

 

KYANITE The name kyanite comes from the Greek work kyanos, which means “blue.” Kyanite grows in a bladed crystal formation. This formation makes it especially popular with mineral collectors. Kyanite is anisotropic, meaning the Mohs hardness depends on the directionality of the crystal when measured – the short dimensionality is harder than the long. Care should be taken not to cause a strike or blow to the stone, to avoid a fracture. Kyanite is sometimes oiled or lubricated for luster, and this should be disclosed. Moss kyanite is a variety with dark inclusions, and is typically a greener blue than “normal” silvery blue kyanite. Rarely, kyanite can be yellow, orange, or pink.

 

LABRADORITE Labradorite is a variety of feldspar, just like moonstone – but it is a plagioclase variety while moonstone is orthoclase. Did you know that most “Oregon Sunstone” is simply labradorite, with copper inclusions that give it its burnt orange color? Rainbow moonstone is also a variety of labradorite. Labradorite is famous for its “flash,” or labradorescence, that can be seen when tilting the stone at different angles. This is light reflecting off surfaces where two crystals grew together. It’s named for Labrador, Canada, where it was discovered. Labradorite is not treated.

 

LAPIS LAZULI Lapis lazuli, sometimes called lapiz, is not a single mineral, but is rather made up of blue lazurite, white calcite, and metallic bronze pyrite. Crushed lapis was used as ultramarine paint during the Renaissance – Van Gogh’s famous “Starry Night” was done with this crushed lapis paint. Commonly, lapis is dyed to improve the color, or waxed or oiled to camouflage fissures and cracks. These are industry accepted treatments.

 

LARIMAR Larimar has been taking off in popularity, with good reason. It is a truly unique gem, a rare variety of pectolite, a silicate mineral. It is said that it was initially discovered in 1916, but the permit for mining was denied and the stone forgotten about. It was rediscovered in 1976, at which time it was given the name “larimar,” after Larissa (the daughter of Miguel Medez, one of the discoverers), and the Spanish word for “sea,” mar. To this day, larimar is only found in one mine, in one region of the Dominican Republic. That can make obtaining larmiar outside of the Caribbean challenging and quite costly – but always worth it! Larimar is not treated in any way.

 

LARVIKITE Larvikite, though sometimes incorrectly called “black labradorite,” is not the same material as labradorite. Labradorite is a mineral, and larvikite is a collection of minerals. It does display the same optical phenomenon as labradorite, called “labradorescence,” or “schiller.” This effect is a result of alternating layers of alkali feldspar and plagioclase that make up the stone. Larvikite comes from Norway. It is not treated.

 

LEPIDOCROCITE True lepidocrocite is an iron oxide-hydroxide mineral and is not used in jewelry. The stones commonly sold as lepidocrocite are a colorless mineral with flashy red and sometimes black inclusions. In reality, this stone contains goethite or hematite inclusions in quartz. At some point, someone began calling it “lepidocrocite,” likely thinking the inclusions were lepidocrocite, and the misnomer stuck. This is colloquially known as lepidocrocite, but it is not. To be more transparent, it could be called “lepidocrocite quartz.” To confuse things further, a colorless mineral with red inclusions may also be called “strawberry quartz” or “moss amethyst,” though usually the coloring and patterning is different and determines the terminology used.

 

MALACHITE Malachite gets its’ distinctive green color from its’ copper content. It has been used as a gemstone, and for sculptures, for thousands of years. Historically, it was used as a pigment in paint – a top choice for painters because the color does not fade over time. It commonly intergrows with azurite, turquoise, and chrysocolla. When found in underground cavities, growing as stalactites or botryoidal coatings, and then cut from a slab, it shows beautiful banding and eye patterns. It may be dyed for color.

 

MAZURITE / MALACHITE-AZURITE / AZURE-MALACHITE “Mazurite” is one term used to describe the result when azurite (blue) and malachite (green) grow together. Both stones are copper based and can often be found near copper mines, or mines of copper-based stones like chrysocolla and turquoise. It is unlikely to be treated. About the individual stones:

  • Malachite gets its’ distinctive green color from its’ copper content. It has been used as a gemstone, and for sculptures, for thousands of years. Historically, it was used as a pigment in paint – a top choice for painters because the color does not fade over time. It commonly intergrows with azurite, turquoise, and chrysocolla. When found in underground cavities, growing as stalactites or botryoidal coatings, and then cut from a slab, it shows beautiful banding and eye patterns.
  • Azurite is named for its “azure blue” color. It has been used historically as a pigment, although it doesn’t make a very good one because it is unstable in air. It is possible for azurite to undergo chemical changes and become altered to malachite, while retaining its’ original crystal structure.

  

MOONSTONE The phenomenon that gives moonstone its’ characteristic glow is called adularescence. This light is the result of alternating layers of orthoclase and albite that make up moonstone. Some moonstone has a “chatoyant” effect, creating a cat’s eye-like pattern of light. Rainbow moonstone is a different mineral – it is a variety of plagioclase feldspar, a variety of labradorite. It displays “schiller,” or flashes of colored light. Conventional moonstone may be called “white moonstone” to differentiate it from rainbow moonstone. Other popular varieties of moonstone are peach, gray, and chocolate. Moonstone is not commonly treated.

  • RAINBOW MOONSTONE “Rainbow moonstone” is a different mineral than the stone traditionally called “moonstone” or “orthoclase moonstone.” Conventional moonstone has a milky glow to it, sometimes with a cat’s eye effect, while rainbow moonstone displays flashes of colored light, called “flash,” or “schiller.” This is the result of the light bouncing off a twinning surface – where two layers of mineral meet. Rainbow moonstone is a plagioclase feldspar and is technically a variety of labradorite, which displays a similar light phenomenon. It is not treated.

 

 

Much of the information in this post came from my personal knowledge. I also used www.Mindat.orgwww.Gemdat.orgwww.Geology.comwww.Minerals.net, Wikipedia, and of course www.GIA.edu. I recommend all of these sources as reliable and trustworthy.