Smithsonite, Where Did That Name Come From?

     Does the name of this mineral sound familiar? Smithsonite and the Smithsonian Institute have very similar names and that is because they were both named for the same person: James Smithson. This happened because the man who donated his estate to what is now the Smithsonian also discovered that the mineral calamine was actually two different minerals: smithsonite and zinc oxide.
     Smithsonite crystals are rhombohedra (that means that they have six diamond-shaped faces). Smithsonite in crystalline form is rare, however, and the mineral is more often found as banded stalactites or in botryoidal form. Like many minerals smithsonite is white or colorless when pure, but impurities can cause it to appear to have different colors. In smithsonite the most common colors are: green, purple, blue, brown, yellow, gray, or pink. Smithsonite is translucent (it allows light to shine through it) and is affected by mild acids.
     Smithsonite contains zinc and was used as a zinc ore until the 1800s. The ancient Romans made brass (an alloy or mixture of copper and zinc) by smelting copper ores and smithsonite together. They did not know that smithsonite contained zinc or even that adding zinc to copper made brass, they just knew that they would get brass by smelting those two rocks together. The metal zinc was not discovered until the mid 1700s when a German chemist by the name of Andreas Sigismund Marggraaf discovered it in, you guessed it, smithsonite. Today smithsonite has few uses outside of collecting as it is a little too soft to use in jewelry and better zinc ores have been found. Smithsonite does serve a limited use as a decorative stone and it can be ground to make fertilizer for agriculture.
     Smithsonite is found in such places as: Italy, Poland, Australia, Brazil, Bolivia, Japan, Zambia, Argentina, Greece, and Morocco.

Vanadinite, Please, Sir, May I 'Ave Some Ore?

     Vanadinite is one of my favorite minerals, and it brings me great pleasure to write about it today. Hopefully after reading this, vanadinite will be one of your favorite minerals as well.
     Vanadinite crystals are very simple, but they are still quite stunning. They are hexagonal prisms like quartz, but they don’t have the pointy ends that quartz crystals do. If you will, they are like six-sided cylinders. Vanadinite is of a bright orange-red color and can be translucent or transparent. Vanadinite is very shiny, so shiny that it will sparkle when turned about in the sunlight. Vanadinite’s luster (the rock and mineral-world term for the way a mineral reflects sunlight) is described as adamantine. That means that its luster can be compared to that of a diamond!
     Vanadinite has served as an ore of two different metals: lead and vanadium. Lead once had a lot of uses, but today, since we have discovered that it is poisonous, it serves far fewer (read more about the uses of lead in my Dec. 16, 2010 post Galena, Beautifal, but Dangerous) Vanadium is used primarily to strengthen steel by alloying (mixing metals.) Vanadium is added to steel to make it stronger and less likely to rust. Vanadium steels are used to make such things as car parts, tools, and knives. And, as I have suspected for a long time, vanadinite is named for vanadium.
     Vanadinite is found in such places as: Arizona, Nevada, New Mexico, Mexico, Scotland, Austria, Zambia, and Morocco. One other very specific source is Custer County, South Dakota. I have done some rock collecting in Custer County, but I did not find any vanadinite while doing so.
     Vanadinite has a lot of traits that I find most desirable in a mineral. It is rare, it is beautiful, it contains lesser-known elements in its chemical makeup, and it has some technological uses. No wonder vanadinite is one of my favorites!

Fluorapophyllite--That's an Odd Name!

     Fluorapophyllite certainly does have a strange name. Believe it or not its name is actually quite new. Fluorapophyllite belongs to a group of minerals that were all once thought to be one mineral, which was called apophyllite. When scientists realized that these minerals slightly differed because of their chemical makeup they renamed the individual minerals and the name "apophyllite" was given to the mineral group. The individual apophyllite minerals were renamed by combining the name apophyllite with the name of the chemical component that is unique to the individual mineral. For example, the apophyllite mineral that was rich in fluorine was renamed fluorapophyllite. The name apophyllite is composed of the Greek words apo, meaning “off” or “detached” and phyllon, meaning “leaf.” It was given this name because of its tendency to flake apart when heated.
     Fluorapophyllite has a very complex crystal structure. One form of fluorapophyllite crystal looks like a six-sided die that has had all of its faces’ corners cut off. The other looks like an octahedral prism (that is, it looks like two pyramids connected at the base.) The caps of these pyramids are intact, but all other corners are cut off. Fluorapophyllite is either translucent or transparent and is usually white or colorless. It can also be pale green, gray, yellow, or red. When broken or cut, fluorapophyllite can reflect sun in such a way as to have a grayish blue, pearly luster; so it is sometimes called “fish-eye stone.”
     Fluorapophyllite has no technological uses and has only limited use in jewelry. The only real use that people have discovered for the mineral is as a nice addition to rock and mineral collections.
     Fluorapophyllite is an unusual mineral, but in my opinion “unusual” can be just another word for “intriguing.” Fluorapophyllite is certainly intriguing…now if we could just come up with name for it that’s easier to spell!

Malachite: the Beautifal Rust

     Malachite is a green mineral that is formed by the chemical weathering of copper; basically it is copper rust. If you have ever watched a piece of copper turn orange, then brown, and then green you have witnessed the formation of the mineral malachite. The malachite that people find in the ground is formed the same way and often grows on top of natural copper deposits. This malachite often forms in layers and can eventually become quite thick. When malachite of this nature is cut open a certain way it looks like a green agate with bands that alternate between light and dark green. The layers of malachite may be of varying hues, but its color does not alter: all malachite is green. In addition to forming as a rust on copper, malachite can also be found as nodules, botryoidal aggregations, and stalactites, as well as monoclinic crystals. A lot of monoclinic crystals that I have seen look like two keys from a keyboard that are fused at the base so that the face that has the letter on it is visible on both keys. I have never seen malachite with individual monoclinic crystals, so I cannot tell you what it looks like. Malachite is opaque (light does not pass through it) and it is often found with azurite, which is another copper mineral.
     Malachite has been used as a copper ore for some time and still serves as one today, but it is not used as often as other ores since malachite is also a decorative stone. Malachite’s banding makes it a popular stone to polish for such applications as cabochons, slabs, and boxes as well as carvings. It is used to make jewelry, but its polish will scratch very easily as it is very soft. Malachite can also be crushed to make pigment.
     Malachite can be found wherever copper is mined or exposed to the air (you can probably find malachite under your sink if your pipes are slightly corroded) Some places where malachite can be found in the ground and in the rocks are Arizona, Russia, Zaire, and Namibia.
     Malachite is one of the fastest-forming minerals that I know of. Simply place a piece of copper outside, let it get rained on a little, and you’ll have malachite growing after a little while. It might seem strange to say it, but rust can be beautiful!

Pumice: the Rock that Floats

     Have you ever heard the phrase, “sink like a rock?” I am sure that you have, and it makes sense, because most rocks are so dense that the idea of one of them floating would seem completely ludicrous. However, you will soon see that the phrase, "sink like a rock" does not ring true in the case of every rock.
     Pumice is a natural glass that is formed by volcanoes. When molten rock erupts from a volcano it can form a number of different rocks under different circumstances. Sometimes when this molten rock cools quickly it forms natural glass, a substance that is a lot like the glass that we use for making jars and windows, but is made by natural processes, like obsidian. Pumice is formed this way, but unlike obsidian, which is dense and has very sharp edges, pumice is filled with bubbles of gas and is very light. When this gas escapes the bubbles leave a lot of tiny void spaces in the rock and thus pumice is formed. Pumice has no regular shape, but is rather found as amorphous pieces of hardened lava-froth. Pumice is usually white or gray in color, but other color varieties do exist. The color of pumice really depends upon what kind of rock was melted to make it. Pumice that is composed mostly of rhyolite or trachyte is white, pumice that is composed mostly of andesite is yellow or brown, and pumice that is mostly composed of basalt is pitch-black. As I have said before, the bubbles found in pumice make it very lightweight. Pumice is so light, in fact, that it will actually float in water!
     Pumice is used to make gentle abrasives such as Lava Soap, a brand of liquid hand soap that contains small pieces of pumice that help to scrub grime off of one’s hands. You can buy blocks of pumice to remove calluses from your feet, as the porous volcanic glass will act as sandpaper against the dead skin while having no ill effect on your living tissue other than some minor discomfort. One interesting use for pumice that I have seen is as a landscaping stone. At the gardening section of a certain hardware store I once saw boulders of pumice for sale that measured about two feet across. They were supposed to imitate other sorts of stones in landscaping applications. These were somewhat comical, because while they looked like small boulders I could lift them with ease.
     Being a volcanic rock pumice can be found, theoretically, wherever volcanoes are present. There are large sources of pumice, however, which include: Italy, Turkey, Spain, Greece, and the United States in the Rocky Mountains and the Pacific Coast. Interestingly, pumice can sometimes travel far from its source. Since pumice can float on water for months before it becomes waterlogged and sinks, any pumice that was formed near the ocean can drift to wherever the currents may carry it. After the eruption of Krakatoa large pieces of pumice floated about in the Indian Ocean for months. The pumice from Krakatoa floating about in the ocean actually posed a hazard to ships for a little while afterword.
     Pumice is certainly one of the coolest rocks that I know of, after all, how many rocks do you know of that can float? Perhaps rock and mineral collectors can coin a new phrase, “sink's like most rocks.”

Chrysoprase, the Gem of Kings

     Chrysoprase is an apple-green variety of the mineral chalcedony. Chalcedony is a variety of microcrystalline quartz (that is, quartz that is composed of a lot of tiny crystals as opposed to a single large crystal) Chrysoprase gets its green color from nickel impurities. This color can fade when chrysoprase is heated and when it is displayed in direct sunlight, so if you happen to have a piece, don't display it in the sun for prolonged periods of time! Being microcrystalline chrysoprase has no shape, but rather is found as veins and nodules. Once source of information that I read said that chrysoprase belongs to the hexagonal crystal group, but I believe that that description refers to the tiny crystals that make up its mass and not to the mass itself. Chrysoprase is translucent, but can be nearly opaque and while chrysoprase is known for its common apple-green color it can also be yellow-green in rare occasions.
     Because of its attractive color chrysoprase has been used as a gemstone since ancient times. Chrysoprase is still used as a gemstone today.
     Possibly the most famous source of chrysoprase is the region of Silesia in Poland. This source has been used since medieval times and some of its gems were used to make jewelry for kings, most notably King Frederick II of Prussia. King Frederick even discovered a vein of chrysoprase there that was three miles long! Since the source in Poland has been just about exhausted the market has turned to other sources. Today most chrysoprase comes from Australia. Other sources include: Russia, Germany, Tanzania, Kazakhstan, Japan, Arizona, and California.
     I think that chrysoprase is a beautiful stone, and it appears that others agree! Chrysoprase has been used by the Ancient Egyptians, the Ancient Greeks, the Romans, and the king of Prussia. However, One greater than all of those previously mentioned has made use of chrysoprase as well. In the book of Revelation God has revealed to us that He plans to use chrysoprase as a foundation in the New Jerusalem. Chrysoprase is truly the gem of kings, and of the King of kings!

Mica: a Shining Star

     The term "mica" actually refers to a group of minerals. These are part of a group of minerals geologists call “rock forming minerals” because they are one of the main components of many types of rocks. Certain types of granite, for instance, contain micas.
      Micas are chemically similar and all possess similar properties. Their crystals are made up of many layers of thin sheets that resemble the pages of a book and can be split very easily. Mica crystals are technically monoclinic, which, without the scientific definition, means they have ten faces, are very thin, and look somewhat like two keys from a desktop-computer’s keyboard fused at the base to make a single shape. These crystals usually have six sides. In rare cases people have found mica with twinned crystals that looked like five-pointed stars. However, micas are so soft that their six-sided, monoclinic shape is often distorted, or at least all of the specimens that I found had been. Individual mica crystals can be very large, the largest ever found measured thirteen feet across! The color of different mica minerals depends on their chemical composition. While there are currently more than twenty micas identified, I wall only cover the most common: muscovite is usually colorless, but is sometimes pale green; biotite is jet-black, phlogopite is colorless or brown, and lepidolite is violet-pink. Mica also has a very reflective surface. I learned this first-hand while driving through a campground at night in a place where small fragments of mica littered the ground. As the light from the car headlights struck the pieces of mica they seemed to glow. At the time I did not know a great deal about mica and it wasn’t until the next morning that I found out what the little glowing things were!
     In industry large sheets of mica are called sheet mica, and small flakes are called flake mica or scrap mica. Sheet mica was once used to make machine parts since it is not flammable, but I think that other substances have replaced it in that application by now. In today’s industry sheet mica is used as an insulator in electrical applications because it does not conduct electricity. Given mica’s shiny surface, flake mica is ground and used to give wallpaper a shiner luster. Perhaps the most interesting use that I have seen for mica comes from the Muscovy province in Russia. There, people once used large sheets of muscovite mica (which was named for the province, by the way) as a substitute for glass in the windows of their homes!
     Since they are rock-forming minerals, micas are found all over the world in igneous, sedimentary, and metamorphic rocks. Some good sources of sheet mica include: India, Brazil, and Madagascar. Some good sources of flake mica include: North Carolina, New Mexico, and South Dakota.
     Because it is used in today’s industry and is one of the major components in many rocks, the micas are certainly important minerals. Some are quite literally shining stars!