Category: Mineral of the Month

 

A new, but very small deposit of Polychrome Jasper has recently been found in the deserts of Madagascar. Specimens from this deposit were first sold at the Denver Gem and Mineral Show last September. Since I was going to the Tucson Show, I was commissioned to purchase larger and unusual mineral art specimens from friends who live in Lansing, MI. This was an awesome responsibility, but I enjoyed searching for and negotiating the purchase of higher-end specimens. As soon as I saw the Polychrome Jasper, I knew I had to add this to the list.

Polychrome jasper is a type of opaque, multi-colored chalcedony which develops in massive formations. Unfortunately, the formations found in Madagascar are few in number. It also goes by the name of Royal Savannah Jasper and Desert Jasper. It is believed to be one of the rarest jaspers in the world. In addition to the new pockets found in Madagascar, some deposits are also located in Australia.

Like other chalcedony minerals, it is thought to be a protective stone that improves self assurance and confidence. It can also help to foster a positive attitude. Professional guitar players are familiar with the stone because Polychrome Jasper is used to make high-quality guitar picks.

The featured mineral this month is what I call Sea Shell Jasper. Others call it Shell Jasper, or Shell Marble Jasper. It is a new mineral that comes from China. Although it is marketed as jasper, it is actually marble. It has beautiful mottled black, white, and gray colored patterns that appear as a conglomerate group of fossils. However, it is metamorphosed marble consisting of mostly calcite with swirls of limestone, chert, and other impurities. One indicator that this rock is not jasper is that it is relatively soft with a hardness of 4. Despite its softness, it takes a nice polish.

This marbleized “jasper” is valued as a sacred and powerful stone that offers grounding and protection. It can help to invigorate and strengthen your physical, mental, and spiritual being.

 

Jasper is a form of microcrystaline quartz. Its name comes from the Greek word, iaspis, which means “Spotted Stone.” Jasper comes in many colors and patterns, but is most often red, brown, or green. Jasper is what I refer to as a “First Cousin” to agate. Both semiprecious stones are microcrystaline quartz. The difference between them is the size and shape of the quartz microcrystals. Those in jasper are small, round grains of quartz crystal, which pack together tightly like bee-bees in a jar. Thus, jasper is usually opaque. Agate, on the other hand, has slightly larger fibrous quartz crystals, which results in it being translucent in most cases.

Many jaspers are actually metamorphic rocks. In cases like Picture Jasper, the colorful patterns result from other minerals that are present in the specimen. Picture Jasper primarily comes from Idaho and Oregon. It formed when mud rich with quartz oozed and dripped into pockets of gas formed by molten lava. The heat from the exposure turned the mud solid almost instantly. Therefore, Picture Jasper is actually petrified or silicified mud. Because of its interesting patterns, it has been used as a psychological tool: the researcher will ask a client who is “looking for an answer” to gaze into the stone and describe all the symbols he sees. The researcher then works with the client to form the symbols into some sort of answer. Picture jasper is said to help with the re-evaluation of life’s issues. It is also believed to facilitate development and continuance of business pursuits and activities. It can also be used in meditation to encourage balance, as well as to help you to improve your self confidence and courage.

This yellow-green mineral is found throughout the world, but most notably in Australia, South Africa, Germany, and the United States. The specimen featured this month was found in the Keeweenaw Peninsula in Michigan’s Upper Peninsula. It not only includes crystals of Prehnite, but also specs of copper, calcite, and silver. It forms near the surface of basaltic lava flows and often occurs in geodes or veins. It forms as a result of low grade metamorphism from hydrothermal solutions.

Prehnite can be confused with gyrolite, smithsonite, and hemimorphite. It can be distinguished because it is harder than these other three minerals. Smithsonite has more of a vitreous or pearly luster and hemimorphite is usually bluer in color while gyrolite is not as glassy.

Prehnite is a phyllosilicate of calcium and aluminum with the formula: Ca₂Al(AlSi₃O₁₀)(OH)₂. It is brittle with an uneven fracture and a slight vitreous luster with a white streak. It has a hardness of 6 to 6.5, with an average specific gravity of 2.80-2.90. It is translucent with a color that varies from light green to grey, yellow, or white. When heated, this mineral gives up water but will not take the water back up when cooled.

Phrenite was first discovered in South Africa by Colonel Hendrik Von Prehn, an early Dutch governor of the Cape of Good Hope colony. It was the first mineral to be named after a person.

Its metaphysical properties are thought to enhance energy, provide protection, and promote calmness. It is also used to advance the state of meditation and help you to remember your dreams.

Mexican Opal comes from the Magdalena, Jalisco area of Mexico. Historians have determined that the Aztec people used Mexican opal for ceremonial and ornamental purposes between 1200 and the early 1500s when the Spaniards Conquistadors took over the area. It is known by locals as vitzitziltecpal or the “humming bird stone” due to the iridescent similarity to the feathers of the bird. It also has several other local names including fire opal, jelly opal, crystal opal, cherry opal, and girasol. Many ancients believed that the storm god became jealous of the beauty of the rainbow god. As a result, the storm god broke the rainbow, causing pieces of the rainbow to fall to the Earth to become a part of the opal which exhibits the “rainbow-fire” appearance.

After the Spanish took over the area, the source of these opals was lost until 1840 when Sir Jose Maria Siurab discovered the deposits. Mining still continues today, but the number of opals found has dwindled since the peak production in the late 1960s.

All opals are hydrated silicates containing between 3 and 10 percent water. Some, but not all opals, have a “play of color.” This color show results from diffraction and interference of light rays that travel through the spaces between columns of microcrystaline spheres of silica. The diameter of the spheres within any column determines the resultant color. If there is no color, as is true with common opal, there is a random pattern of microcrystaline spheres, and thus, no structure to act as a diffraction grating.

The specimen featured this month was purchased from a small rock shop located just outside of Yosemite National Park during the late 1990s. I had just finished hiking with my friend, Clare Comstock, when she spotted the rock shop. This six pound gem was on display as an example of opal from a Mexican mine operated by the rock shop’s owner. When I saw the specimen, I asked about its availability for purchase. Although the owner said it was not for sale, she finally agreed to part with it as long as I agreed to display it prominently in the museum. Not only have I done that, but now I’m featuring it as the Mineral of the Month.

I have left this specimen raw because of its innate beauty. Plus, opal can be somewhat fragile and has a tendency to develop fine cracks due to dehydration. I only “dress up” and polish rocks if it will increase the value of the specimen. For this beauty, it is not worth the risk.

Gemological Data
Chemistry:	hydrated silicon dioxide
Luster:	vitreous to resinous
Hardness:	5.5 – 6
Crystal structure:	none, it is amorphous
Fracture:	conchoidal to uneven
Cleavage:	none
Density:	2.15
RI:	1.42 – 1.43
Birefringence:	none

Metaphysical Properties

Opal helps with the amplification of your most positive traits, therefore, providing the ability to overcome your lesser attributes. It can also improve your creative flow and maximize your inspiration and imagination. Opal has been used by the Native American Indians and the Australian aboriginal shaman to invoke visions and to facilitate ceremonial “dreamtime.”

Technically “Mohawkite” is not a mineral but is a combination of copper arsenates with nickel and cobalt. It is also considered a variety of Domeykite. It is named after the original locality: the Mohawk Mine located in the Keeweenaw Peninsula of Michigan’s Upper Peninsula. This is the only location in the world that Mohawkite is found. The cubic crystals are rare in that the mineral more typically forms in masses, especially filling veins in hydrothermal vents. On a freshly fractured or mined surface, it appears whitish, but quickly tarnishes to brown. Sometimes the oxidized surface appears to have iridescence as it tarnishes. It has a hardness of between 3 and 3.5 with a specific gravity of between 7.2 and 7.9. It has a metallic luster with a brownish streak. Because of its speckled formation and combination of minerals, it has an uneven fracture. It is believed that the nickel arsenides crystallized first at higher temperatures. Later, fracturing occurred and some of the nickel was replaced by the copper arsenides-bearing solutions.

The mineral of the month for the summer 2008 update is Marra Mamba Tiger’s Eye. This mineral is found in western Australia, near Mount Brockman, but is thought to have been mined out over a decade ago. It forms when silica quartz replaces crocidolite (asbestiform riebeckite). Marra Mamba tiger’s Eye is known for its quality because it also contains red jasper, yellow chert, and black magnetite. I call it the psychology rock because people see different images in its chatoyant patterns. The fibrous nature of its parallel banded structure causes light to reflect through the layers, that roughly resembles the eyes of tigers or hawks. When there is enough magnetite in a specimen, it can be magnetic.

Other locations for tiger’s eye include South Africa, India, Myanmar, Sri Lanka, China, Brazil, Namibia, and California.

Tiger’s Eye is the planetary stone for Gemini (May 21 – June 20), and the celebratory gem stone for the ninth wedding anniversary.

It is thought by some to help with health and spiritual well being. Others believe that it is a psychic protector, aids in business, and helps one to achieve clarity.

At the request of a customer, I am going to again feature Ocean Jasper as the Mineral of the Month. Ocean Jasper made an appearance on the original web page several years ago, but it deserves to come back.

Until I completed an Internet search about Ocean Jasper while preparing this web page update, I wasn’t sure exactly when I first saw Ocean Jasper. Now I realize that it was at the Denver Show in 2000. I remember that I was visiting the exhibits housed in motel rooms. As I walked down the corridor, I passed a room that had a slab of Ocean Jasper that was six foot tall! It stopped me in my tracks! Although their high prices were appropriate given that it was a brand new mineral, I thought I would be smart and check out the Ebay prices when I returned home. I was successful in purchasing some of the magnificent mineral, but I paid for it. I bought the two specimens below from a couple in Great Britain. I paid $150 for the round slab and $75 for the egg. However, they are still two of my favorite pieces of Ocean Jasper. Notice the chrysoprase band in the round specimen and the agate pockets in the pink egg-like specimen.

 

I also must correct the historical information about this mineral that I have been presenting at the museum. I was told years ago that it was discovered eight years ago by two guys who were rock-climbing on the northern coast of Madagascar. Instead, it appears that the mineral had been discovered at the early part of last century. An article appeared about the unusual mineral in 1922. Then, the mineral was basically lost to the world for over 70 years. In 1997, the Mineralogical Encyclopedia (GRUND Publisher) reproduced a picture of the mysterious jasper showing the orbicular structures. The caption for the photo said that the source of the mineral was unknown. This picture excited rockhounds, including the field explorers for Madagascar Minerals who launched an expedition to locate the source. Their first attempt failed, so they regrouped and decided to methodically search the entire northern coastline of Madagascar. They spent 45 days navigating the coast, stopping in villages to ask locals if they were familiar with the mineral. Finally, they found the 50 x 30 yard deposit in shallow water in a remote area, It could only be seen and mined during low tide. The company had to work from boats, since the isolated region is not near a town and has no road access.

It is rare for new minerals to be discovered in this well-traveled world. Usually, new materials brought to market are usually just new deposits of already known minerals. However, Ocean Jasper is an exception.

It is thought that Ocean Jasper formed as a rhyolitic igneous rock, rich in silica. As the lava cooled, the silica precipitated out of the magma, forming little spherical balls. Later, the entire formation converted to pure silica made up of a combination of microcrystaline agate and jasper, as well as macrocrystaline quartz. The small deposit contains a wide array of color including white, green, red, yellow, and pink. There are also botryoidal and druzy quartz formations throughout the matrix. The genesis of the orbs in this beautiful rock is not known. However, research is being conducted at the University of California at Berkley to try to uncover the mystery.

The mineral is also known as Orbicular Jasper and Fish Eye Jasper. Similar, but less dramatic jaspers are found elsewhere in the world including Poppy Jasper from Morgan Hill in Santa Clara County in California and Rain Forest Jasper from Australia.

The metaphysical properties of Ocean Jasper are thought to: enhance one’s joy, help you better connect in loving relationships, improve cooperation, and help you focus on the positive aspects of life.

The mineral of the month for May 2008 is Apophylite. This specimen was acquired from a Brazilian dealer who was liquefying his entire inventory at the Tucson show a couple of years ago. He said something about wanting to go fishing. Apophyllite is in the Silicate class of minerals, which tend to be translucent and are lower in specific gravity and harder than most minerals. All silicates contain the silicate atomic structure, whose fundamental building block is the tetrahedron, in which one silicon atom is surrounded by four equally spaced oxygen atoms. Other silicates include quartz, chalcedony, opal, orthoclase feldspar, and amazonite.

Apophyllite is a hydrous calcium potassium fluorsilicate. It can either be colorless or white, gray, green, yellow, or red. It has a hardness of 4 ½ to 5, a specific gravity of 2.3, and has perfect cleavage in one direction. The crystals are tetragonal, usually cube like or tabular and square in cross section. It forms at low temperatures and is commonly found in cavities in basaltic pockets, where it is often associated with zeolites and prehnite. Although this specimen is from Brazil, Apophyllite can be found in the copper mines on the Keweenaw Peninsula among other places world-wide.

The name, Apophyllite, means “to leaf apart” in Greek. The name derived from the tendency of the crystals to peel off when specimens are heated due to the sudden loss of water molecules within the structure. Although collectors refer to this mineral is Apophyllite, it is no longer officially classified as a mineral. Originally, the group name referred to a specific mineral, but was redefined in 1978 to stand for a class of minerals of similar chemical makeup. Apophyllites are popular as with collectors due to their well-defined crystals, color, and abundance.

The metaphysical properties of Apophyllite are thought to enhance your analytical skills and enable you to act in a truthful and honest manner. It can also be used to help you evaluate your behaviors and attitudes so that you can identify and correct any shortcomings.

The mineral of the month is my favorite agate: the shadow agate. This specimen was picked up off the Grand Marais beach by the museum founder, Axel Niemi. He found it in 1925 when he was just eight years old. He had it for almost 40 years when he finally sliced the agate, discovering the intricate banding. The best shadow agates in the world come from Lake Superior, Botswana Africa, and Queensland Australia.

Shadow agates exhibit an optical effect of movement across the bands. Depth is perceived from light penetrating and bouncing between alternating clear and opaque layers. When you move these agates back and forth, shadows can be seen racing across the surface. Many factors contribute to the shadow phenomenon including the regularity, contrast, distance, and depth of the bands. When the right conditions exist, light disappears into the clear chalcedony bands and is not reflected back out to the eye. When little or no light is returned to the line of sight, we interpret this as a dark region, or shadow.