Varieties of Quartz; Chalcedony, Geode, Jasper, Agate

Posted by Elisabeth Dignan on

QUARTZ Quartz is the second most abundant mineral in earth’s crust, and some well-known varieties include citrine, amethyst, and prasiolite. The word “quartz” comes from the Greek kruos, meaning “icy cold.” The Greeks believed quartz was a supercooled form of ice. It is used in many forms of technology due to its pyroelectric properties (it reacts to temperature change with positive or negative charges).

 

  • CHALCEDONY Chalcedony is a microcrystalline variety of the mineral quartz. It is translucent to opaque and can be almost any color, but naturally it is often white-to-blue, bluish-gray, or brown-to-black. Many well-known stones such as agate, jasper, carnelian, and onyx, are actually types of chalcedony. Chalcedony has been used by people since at least 1800BC. It holds dye fairly well, and the bright colors of chalcedony, as well as the ever-popular aqua chalcedony, are the result of this treatment. It can be heated to create carnelian. When dyed green it is called 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.

 

  • ROCK CRYSTAL Quartz is the second most abundant mineral in earth’s crust, and some varieties include citrine, amethyst, and prasiolite. The word “quartz” comes from the Greek kruos, meaning “icy cold.” The Greeks believed quartz was a supercooled form of ice. While quartz comes in virtually any color, colorless quartz is known as “rock crystal.”

 

  • ROSE QUARTZ Rose quartz is a cloudy translucent pink variety of quartz. It is abundant and found in many locations all over the world. It’s highly cherished in the healing crystal community, notably for its effect on unconditional love. The hue of rose quartz is so treasured that it was the Pantone color of the year in 2016! It may be irradiated for color.

 

  • RUTILATED/TOURMALINATED QUARTZ Rutilated quartz and tourmalinated (or tourmalated) quartz are similar and often confused. Rutilated quartz inclusions are rutile (titanium oxide), while tourmalinated quartz inclusions are tourmaline – just as the names suggest. It is important to distinguish correctly between the two. Rutiles are golden to brown to reddish golden, while tourmaline inclusions are typically black. While inclusions usually lessen the value of a gemstone, in these cases they are treasured.

 

  • SMOKY QUARTZ As the name implies, smoky quartz is a variety of quartz. Quartz is a silicon dioxide crystal, and smoky quartz occurs when quartz is irradiated or heated, which results in free silicon. This can be natural or artificial.

 

  • SOLAR QUARTZ Solar quartz is agatized quartz, cut from stalactites. It can be clear, white, or gray, and has mossy inclusions in a variety of earthy hues. Occasionally amethyst grows around the outside edges, creating a purple ring around the core. Solar quartz is often dyed bright colors.

 

  • FRUIT “QUARTZ” Colorless materials with various colored “inclusions,” such as “cherry quartz,” “blueberry quartz,” “pineapple quartz,” “strawberry quartz,” etc. Almost all materials sold under these names are simply synthetic materials, commonly glass. Care should be taken when purchasing, if natural material is desired.

 

  • STRAWBERRY QUARTZ Natural strawberry quartz gets its color from iron oxide inclusions. The inclusions often look vein-like. Most often however, strawberry quartz is a synthetic material, typically glass, and is disingenuously sold as natural.

 

  • TANGERINE QUARTZ Real tangerine quartz is natural, unlike most “fruit quartz.” It is a red to orange variety of natural quartz, which gets its color from trace amounts of iron oxide. It is likely that all tangerine quartz comes from a single mine in Brazil.

 

 

GEODE with DRUZY/DRUSY Not really a gemstone, geodes are still an incredible material to add to any jewelry. The form as a more or less rounded structure within igneous or sedimentary rocks. After rock around the outside hardens, a slow feed of dissolved silicates and/or carbonates from groundwater or hydrothermal solutions allows crystals to form within the quasi-spherical rock. Most geodes contain clear quartz crystals. A layer of crystals that line the interior cavity is called druzy, sometimes spelled “drusy.” Some geodes contain agate, chalcedony, jasper, or varieties of crystals besides quartz. The shell is commonly chalcedony. If you find a geode with unusual coloring, it is more than likely dyed as this is a relatively common practice. The name “geode” is Greek for “earthlike.”

 

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 actually 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.

 

AGATE Agate, like jasper, is a variety of chalcedony. The difference being that agate is semitransparent, while jasper is opaque. Agate is also banded, meaning color appears in stripes, or bands. There are many, many, types of agate. It is sometimes dyed different colors. Moss and dendritic agate are two types that are not “true” agate, since they aren’t banded, but are called so because they contain multiple colors. Green hornblende inclusions give the mossy appearance in moss agate, and dendritic agate has tree- or fern-like inclusions.

 

  • MOSS AGATE and MOSS QUARTZ describe a quartz-variety mineral with moss-like inclusions. It tends to be called agate when the matrix is opaque or semitranslucent, and quartz when the matrix is transparent colorless. Moss agate is not “true” agate, since it isn’t banded, but it is called so because it contains multiple colors. Green hornblende inclusions give the mossy appearance in moss agate. Despite its name, moss agate/quartz does not contain organic material. It is usually formed in weathered volcanic rocks.

 

 

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