Alaska's State Gem EarthCache

The Official State Gem of Alaska:

Alaska designated jade as the official state gem in 1968 (jade is also the official gemstone of Wyoming). Alaska has large deposits of this gemstone, including an entire mountain of jade on the Seward Peninsula. Prior to English exploration in the late 1700's, native Eskimos traded jade (as well as copper, hides and furs).

What is jade?

Jade refers to an ornamental mineral, mostly known for its green varieties. It can refer to either of two different minerals: nephrite, (a silicate of calcium and magnesium in the pyroxene group of minerals), or jadeite, (a silicate of sodium and aluminum in the amphibole group of minerals).  Jade is featured prominently in East, South, and Southeast Asian art, but also has an important place in many other cultures.

Nephrite or Jadeite?

It was not until 1863 that French mineralogist Alexis Damour determined that what was referred to as "jade" could in fact be one of two different minerals, either nephrite or jadeite. 

Nephrite- consists of a microcrystalline interlocking fibrous matrix of the calcium, magnesium-iron rich amphibole mineral series tremolite (calcium-magnesium)-ferroactinolite (calcium-magnesium-iron). The middle member of this series with an intermediate composition is called actinolite (the silky fibrous mineral form is one form of asbestos). The higher the iron content, the greener the color. Tremolite occurs in metamorphosed dolomitic limestones and Actinolite in metamorphic greenschists/glaucophane schists.

Jadeite- is a sodium and aluminum-rich pyroxene. This, the more precious kind of jade is a microcrystalline interlocking growth of crystals. It only occurs in metamorphic rocks.

Both nephrite and jadeite were used from prehistoric periods for hardstone carving. Jadeite has about the same hardness (between 6.0 and 7.0 Mohs hardness) as quartz, while nephrite is slightly softer (6.0 to 6.5) and so can be worked with quartz or garnet sand, and polished with bamboo or even ground jade. However, nephrite is tougher and more resistant to breakage.

Geological Terms:

• Transparency: light can pass easily through a rock or mineral.  In other words, the rock is completely see-through.

•  Translucency: light can pass through the rock/mineral, but it is diffused.

• Opaqueness: no light can pass through the rock/mineral.

• Cleavage: the rock/mineral breaks along a smooth, relatively flat surface.

• Fracture: the rock/mineral breaks along irregular and pointed edges.

• Luster: the way that a rock/mineral gives off light.  There are two main types of luster.  Metallic luster resembles the way that metals give off light (ie: the mineral pyrite has a metallic luster).  Nonmetallic luster is associated with rocks/minerals that do not resemble a metal.

Logging Tasks:

1. Using the information sign at the GZ, where was this piece of jade found? 

2. Determine if this specimen is composed of nephrite or jadeite.

3. Describe the appearance of this piece of jade.  Note the following below:

• Is the mineral transparent, translucent, or opaque?

• Does this specimen of jade have cleavage or fractures in the mineral?

• What type of luster does this piece of jade have?

• What is the color of this specimen?

4. As of June 2019, earthcaches are now allowed to have a required photo logging task.  Please provide a photo of yourself, your GPSr, or a personal item that proves that you have visited this site.  Please post this in your log.

**Geocachers that do not complete all of the necessary logging tasks above will result in a log deletion.**

Congrats to AKLoisandClark for the FTF!

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Sources:

https://statesymbolsusa.org/symbol/alaska/state-gem-or-gemstone/jade

https://en.wikipedia.org/wiki/Jade#The_mineral

https://en.wikipedia.org/wiki/Nephrite

http://www.geologyin.com/2015/11/how-do-geologists-identify-minerals.html

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