Midwest originated specimens
We introduce two specimens originated from Midwest: Pipestone and Quartzite as the examples (photos below). Pipestone (Catlinite) is a brownish red rock found widely in Midwest region such as Frandreau and Sioux Falls in South Dakota, Blue Earth River and Sac County in Iowa, Pipestone, Cottonwood, Watonwan and Nicollet Counties in Minnesota, and Barron County in Wisconsin. Pipestone is stated as a rock by James D. Dana, not a definite mineral species. Color ranges from a brownish red to an ashy tint. Because the rock is rather easy to cut and make shapes, it is used by Native Americans for making ceremonial pipes.
Although quartzite is typically white to grey in color, it often exhibits in various colors such as red and pink which was caused from the impurities. The red quartzite could be found in the Baraboo area in Wisconsin, such as at the quartzite rock cliff at Davil’s Lake state park or Wisconsin Dells. Sioux Quartzite is also known for the similar red to pink in color which is widely found in Minnesota, South Dakota and Iowa.
How they look under the light microscope?
For the specimens between Pipestone and Quartzite, what would you notice the difference? You can touch the surface. Perhaps you feel smooth surface for one specimen and rough surface for the other. How about the color? Do they both look alike dark red to brownish red in color with your eyes? If you look under the microscope, you can observe the differences in color, texture, grain size, and shininess etc. Here are the photos for these two specimens:
In these photos, both specimens are shown in the same magnification (500 μm). You can immediately notice the different size of the particles. Pipestone is observed fine brownish dark red particles which includes silica (SiO2), alumina (Al2O3), ferric oxide (Fe2O3), lime (CaO), sodium carbonate (Na2CO3) and water (H2O)*. On the other hand, Quartzite has translucent larger grains (such as in size=50 to 300 μm) with some impurities of dark red minerals surrounded. The translucent grains are silicon dioxide (SiO2), and the red mineral is hematite (Fe2O3).
References:
*George F. Kunz. Gems and Precious Stone of North America. The Scientific Publishing Co. P.205-210.
Trilobite Calymene Celebra were a group of crab-like animals with hard outer skeletons. It is known for Wisconsin’s state fossil.
Various rocks from the rocky beaches in Upper Peninsula, MI.
Petosky stone is a variety of calcite, and was formed by the fossilization of ancient coral, Hexagonaria. The stone has a distinctive honeycomb pattern. They are found on many beaches of Lake Michigan and Lake Huron. Petosky Stones are the official Michigan State Stone.
Common rocks, minerals and fossils
Amethyst is a variant of Quartz (SiO2). Trivalent iron (Fe3+) is replaced for Si in the center of tetrahedron to give purple in color.
Citrine is a yellow variant of Quartz (SiO2). Color ranges from pale yellow to brown from the impurities of ferric hydroxide (Fe(OH)3).
Rose quartz is also a type of quartz (SiO2). It has pale pink to rose red in color, usually caused from impurities such as titanium (Ti), iron (Fe), or manganese (Mn).
Jade is a rock subtype and many different minerals have been marketed as jade, especially jadeite (Na(Al,Fe3+)Si2O6), nephrite (a rock classification type of actinolite-tremolite series) and serpentine (subgroup of Kaolinite-Serpentine group, D3[Si2O5](OH)4, D=Mg, Fe, Ni, Mn, Al, Zn), but also green quartz, vesuvianite, carbonates, Horndels etc.
Amazonite is a green to blue-green variety of K-feldspar (K(AlSi3O8)), usually microcline but sometimes applied to orthoclase. The color is usually caused by an elevated content of Pb (up to 1.2% PbO).
Carnelian is a reddish variety of calcedony (variety of quartz, SiO2).
Tiger eye is a metamorphic rock with a golden to brown in color and silky lustre. Also a member of quartz group (SiO2).
Obsidian is an igneous rock that naturally occurring volcanic glass from lava extrusion from a volcano. The crystal is translucent, black in color.
Jet is a hard gem-quality hydrocarbon, but not an approved mineral species. The name “Jet” is applied to material with similar appearance and properties worldwide that may have been formed through different processes.
Goldstone is a type of synthesized glass. It looks glittering, and the finished product could have a smooth polished surface.
Jasper is a type of quartz/chalcedony (SiO2) with varying impurities which results different colors such as red, yellow, brown, green or blue.
another variation of Jasper in yellow and grey in color.
Himalayan salt is a rock salt (Halite, NaCl) with trace of impurities such as calcium (Ca), iron (Fe), Zinc (Zn), chromium (Cr), and sulfate (S) which creates various colors in pink to dark red. It is commonly used as a table salt.
Chalcedony is a variety of quartz (SiO2) in white, grey, blue or any color due to embedded minerals. Most chalcedony contains small amount of Moganite (SiO2), usually between 1%-20%, and water (H2O).
Malachite (Cu2(CO3)(OH)2) is a green, very common secondary copper (Cu) mineral with a widely variable habit. It is isostructure to Chukanovite (Fe2+2(CO3)(OH)2) which exhibits in pale green to colorless brownish green and brown.
Selenite (CaSO4 · 2H2O) is a variety of Gypsum (CaSO4 · 2H2O). It has colorless, light tints, moon-like white reflections.
Chert is a hard, fine grained sedimentary rock composed of microcrystalline quartz (SiO2). The surface is rather smooth. The color varies from white, gray, brown, grayish brown to rusty red depends on the trace elements present in the rock.
Amber is a mixture of two or more distinct mineral species. Amber comprises macromolecules formed by free radical polymerization of several precursors in the labdane family (C20H38). It has yellow-orange-brown, pale yellow, nearly black in color.
Orthoceras (shell) is a squid-like animal from Silurian period (~425 million years ago). It had tentacles and a straight shell that was divided into many chambers.
Petrified wood is type of fossil wood where the original organic material has been replaced. It has usually replaced by chalcedony or agate, but sometime also by opal, coal, pyrite, calcite, apatite etc.
Ammonite (Ammonoidea) are extinct spiral shelled cephalopods from Devonia to Danian period (409 to 65 million years ago).
Metal specimens
Introducing some common metals and their crystal structures. Analyzing a single crystal of such kind by Single crystal X-ray diffraction technique reveals data to solve the crystal structures.
Fluorescent specimens
Some rocks and minerals, known as the fluorescent minerals, emit light in different colors under ultraviolet (uv) light. When a photon strikes an electron (e.g. in the L-shell in the Figure below), an electron absorbs the energy of a photon and jumps up to a higher orbital (e.g. the M-shell). Then an excited electron falls back to its original ground state by emitting photon energy. Because the absorbed photon energy is emitted to some partial heat as well, the rest of the emitted photon energy is lower than the absorbed energy. In other words, an emitted photon has longer wavelength, such as visible light (=lower energy) than the absorbed energy (such as uv light).
All the following specimens are taken each two types of photos: (Top) the photo with fluorescence under the long ultraviolet light (wavelength=365nm), and (Bottom) with the visible light (380 to 750 nm) to compare the effects.
“Confetti” stone was collected from the Calumet Waterpark Beach, Calumet MI. It looks opal like milky color and fluoresces light blue and yellowish orange under long wave UV light.
Fluorite (CaF2) is a mineral species and a member of Fluorite group. It The color varies in purple, lilac, golden-yellow, green, colorless, blue, pink, champagne, and brown. Tis specimen exhibits light orange and pale-yellow fluorescence under long wave UV light.
This Fluorite (CaF2) from Weardale, England exhibits pale-yellow and light green fluorescence under long wave UV light.
Idrialite or Curtisite is a rare hydrocarbon mineral (approx. chemical formula is C22H14). It fluoresces light blue under long wave UV light.
Willemite (Zn2SiO4) is a mineral species and a member of Phenakite group. Almost all Willemite from Franklin, NJ exhibits a bright green fluorescence under UV light.
Willemite (Zn2SiO4) occurs commonly in granular with Franklinite and Zincite, and often in a Calcite (CaCO3) matrix. This Willemite/calcite from Franklin, NJ exhibits a bright green fluorescence under UV light.
Autunite (Ca(UO2)2(PO4)2 · 10-12H2O) is a mineral species in the Autunite group. It is yellow, greenish-yellow, pale green in color. Autunite is a secondary mineral resulting from the oxidation of primary uranium minerals.
Hyalite (SiO2 · nH2O) is a variety of amorphous Opal (Opal-Amorphous Network) with a glass-like structure. It is colorless, white or creme in color. It often shows a strong green fluorescence in UV light.
Semi-Opal (SiO2 · nH2O) is a impure opal and has milky tone in color. It often shows a strong green fluorescence in UV light.
Willemite is a mineral species and a member of Phenakite group. Chemical formula is Zn2SiO4. It is named after the King of Netherlands, Willem I in 1830. Willemite exhibits a bright green fluorescence under UV light.
Scapolite (Na4Al3Si9O24Cl to Ca4Al6Si6O24CO3) is a solid solution series between two end-members of Marialite and Meionite. Wernerite is an intermediate member of the series. It fluoresces bright orange under long wave ultraviolet light.
Sphalerite (ZnS), also known as blende or zinc blende, is the major ore of zinc. Sphalerite is an important source of rare metals such as gallium (Ga) and indium (In), and the semi-metal germanium (Ge).