I was just reading an old geological survery online.  The subject was Hubbard County geology.  Hubbard county is where I live.  It is quite dull, and not referenced even once in my new Minnesota geology book.  To begin, there is no exposed bedrock.  The line of moraines running east to west may tell a little about the history of the movement of glaciers, to someone who can read the signs.  In the southeast corner there are a few pieces of soft, impure limestone, indicating there might be late cambrian era strata underneath the surface. 

I suppose one could dig deeper and look into the geochemical interaction between ground and lake water.  There are also soil surveys, aerial maps, and charts of bedrock geology.  There is also the study of sediment from lakes that were left behind by melted ice glacier.  

I started reading my new book in earnest.  It is Minnesota's Geology by Ojakangas and Matsch.  I like it better than my old MN geology book, which is really too old, because it has more humor and human interest. 

The first chapter is a briefing about geology in general with just a few specific Minnesota references.   It starts out with an exciting version of how the Minnesota River formed, when a melting glacial lake overflowered and flooded through a valley, eroding it and revealing much older rocks.  This may have occurred twelve thousand years ago.  Some geological dates are mind-boggling;  12 thousand years doesn't seem that long.  Or does it?  Another fact that stood out is that Minnesota doesn't have any gemstones of significance. But collectors can find agates and other quartz minerals that are quite interesting. 

 

Am I a Neanderthal?

On occasion I work for Mechanical Turk.  I do HITs.  HITs are human intelligence tasks that can't be done by artificial intelligence.  I get paid a little now and then.  Today I worked for AccessDNA.  The questionnaire I filled out reminded me that I am a European Caucasian, my relatives had an aneurysm, colon cancer, anemia and depression, and I take a lot of meds.  AccessDNA is a useful site for people planning pregnancies, finding out what they're going to die from, who their father is or if they are indeed a father, and stuff like that.  There are lots of links for people who need help because of their genetic inheritance.  I have also received a promise that I will be notified of DNA souvenirs, gifts, and so on when and if they become available.  A report was generated on me, and I received the summary, which was frustrating and leaves me wondering if there was more.  For some reason the file was corrupted and I had to open it in Appleworks.

 But there was a link on that site that fascinated me.  A scientist is sequencing Neanderthal DNA and so far he concludes that Neanderthal and modern man interbred.  So Neanderthals probably contributed to our gene pool.  That would explain a lot.

more sulfates

There are a few more sulfates covered in mineralogy texts.   Bronchantite is formed by oxidation of copper sulfides in arid areas. It is green. Antlerite is similar to bronchantite but the crystals are more often tabular or fibrous. It is also green.

Glauberite is described as a double salt. It is found in arid areas such as Chile, the dry lakes of California, Egypt, Russia, and India. Its crystals form in salt deposits. It is gray, yellow, or colorless.

Alum is a sulfate with commercial applications. Its most recognizable form is in the styptic pencil.

Got a notice from MN DOT. My rock shop signs have to be replaced, even though to me they look new, to the tune of nearly one thousand dollars.Maybe I will reinvent the rock business, and myself.

 

http://www.oliviahoff.com

barite group of sulfates

The barite group of sulfates includes barite, celestite, and anglesite. Barite is used in paints and papers. It is also added to drilling mud in oil wells to control the specific gravity of the mud. Celestite is found throughout the world, mostly in sedimentary rocks. It is named for its distinct pale blue color. The nicest blues seem to be from Madagascar. Anglesite is usually an alteration product of galena. It is usually mixed with cerussite, a carbonate. It is usually colorless, white or gray but can be yellow, blue or green.

I painted a dinosaur on sandstone today.  An albertosaurus. It was a tyrannosaurid, but smaller than rex. And I am not the worlds best artist.

 

http://www.oliviahoff.com

sulfates

Sulfates are oxygen and sulfur compounded with one or more metals. There are over 150 named varieties, due to the number of possible combinations.  Gypsum is the most common. The distinct varieties are alabaster, selenite, and satinspar. Gyppsum is used in plaster of Paris.

Anhydrite is less common than gypsum. It is associated with salt beds and has a pearly luster. It takes up water and converts to gypsum.

Epsomite is common as epsom salts. It is found in mineral waters and deposits, and contains cobalt, zinc, manganese and nickel.Now to the metaphysical Adularia is called the stone of the Goddess. It is a form of moonstone that can be faceted. It is clear with a beautiful iridescence, and is quite rare Many of the deposits in Sri Lanka have been depletes. Some has been found in the Austrian alps. It is valued as a means of inward journeying and symbolizes tranquility.

 

http://www.oliviahoff.com

 

http://www.oliviahoff.com

nitrates

Nitrates are not geologically widespread, nor are they mineralogically significant, except for two types that are used in explosives and for fertilizer. These are niter, also known as saltpeter, and soda niter.Both are found in Chile. They are water soluble. During the Civil War, the supply from Chile was cut off by the Union army and the Confederacy made use of niter associated with bat guano found in caves in Tennessee.

I am not a student of metaphysics. However, I am grateful to those who use stones and crystals for healing for the resurgence of interest in rocks. Adamite is a zinc arsenate associiated with joy, love, creativity and enthusiasm. Usually it is a bright yellow green. The best specimens are from Mexico and Namibia.

 

http://www.oliviahoff.com

blog problems
I blogged about nitrates and adamite but it looks like the blog builder ate up my work.

miscellaneous carbonates

The miscellaneous carbonates covered in books of mineralogy are azurite and malachite. Both are basic copper carbonates, considered too soft to make good gemstones but their color makes up for their lack of hardness.  Azurite is bright blue and malachite is bright green.; Crystals are rare and both are found as earthy aggregates, sometimes together.

Some other miscellaneous carbonates are natron, trona and hydrozincite. These are soft, water soluble, crusty materials formed by the evaporation of water from lakes. In the case of trona, it is the evaporation of  lakes such as those in Utah, California and Egypt.

A friend has loaned me a beautiful book, The Book of Stones, which delves into the metaphysical and healing aspects of stones and crystals, material with which I am not familiar and which I sometimes look askance at. I may blog about this book, with the constant disclaimer that I really dont understand or subscribe to this philosophy of gems and minerals but I have an open mind.

 

http://www.oliviahoff.com

rock business etc.
My rock business might be perking up a little.  Not sure yet.  In the meantime I do my other work, which is writing articles and short fiction for print publications and the web, housekeeping chores, yard work including gardening, taking care of the animals, and lately, painting pictures.  The pictures fall into several categories:  ones that might enhance my rock business, a few for a church project, some to illustrate stories I write and that I will use if I start up my publishing business again, and some just as a hobby.   And, oh yes, photography...mostly of rocks but also other objects.  I have to use a tripod because my hand isn't steady enough and I can't adjust my camera (not knowledgeable...I'm just a point and shoot photographer).

http://www.oliviahoff.com

aragonite

The aragonite group of carbonates consists of aragonite, witherite, strontianite, and cerussite.Aragonite is another of the minerals that a fossils shell can change to. Some fossil samples are part aragonite and part calcite.

Witherite is found in low temperature hydrothermal veins where galena is the major ore. Strontianite is found with celestite in limestones.Cerussite is also known as white lead ore. It has the highest specific gravity of any carbonate. Now, isnt that interesting?

It is a beautiful sunny day and I think I'll go out and do some rockshop cleaning along with flower planting.

 

http://www.oliviahoff.com

dolomite group

Dolomite is similar to calcite in appearance. It is used in cement and to obtain the raw material magnesium oxide. The dolomite group includes magnesite, which is also a source of magnesium oxide for industry. Rhodochrosite is popular with mineral collectors because of its beautiful pink color but it is quite soft. Ankerite is found with iron bearing rocks at such locations as Guanajuato, Mexico, New York and Nova Scotia.Smithsonite in its porous form is called dry-bone ore. In crystal form it may be glassy or pearly.

 

I'm not sure what I will read or blog about after mineralogy but I am leaning toward dinosaurs or gemology.

I am thinking about writing some flash fiction.

 

http://www.oliviahoff.com

SHOP IS A MESS

My rock shop is in disarray.  Enough said.  Moving right along...  The next mineral group to consider is the carbonates.  There are more than 70 minerals in this classification  but only the calcite and dolomite groups are found in abundance.

 Calcite is very common.  It is the main constituent of limestone.  Many fossils are calcium carbonate skeletons of algae and invertebrates.  Under pressure, limestone turns into the metamorphic rock marble.

Siderite is another member of the group.  It oxidizes into limonite.  I just recently traded for some limonite crystals from England.

more about feldspar

The plagioclase feldspars are a solid solution series.  The end stones are albite and anorthite.  Intermediate specimens include labradorite, a well known gem when it's chatoyant, and bytownite, found in Minnesota.

The feldspathoid group are framework silicates containing less sillica than the feldspars.  These were formed in silica-poor areas and therefore are not found in areas where there is a lot of quartz.  Sodalite belongs to this group.  

Two other related groups are scapolite, which in its yellow form has been used as a gem, and the zeolite group which includes 22 well defined species.  The zeolite group includes stilbite, chabazite and heulandite, all of which form into beautiful crystals.

feldspar etc.

I'm doing some paintings for the alternative birthstones, starting with rose quartz, black onyx, bloodstone, and rock crystal.

The next mineral to take up is feldspar.  Feldspar minerals make up one half of the earth's crust.  Microcline is the most common.  This is your familiar pink, green etc. types.  What is different about these that the ions are ordered rather than disordered.  The ordering process occurs as microcline, which is formed under high temperatures, cools.  Sanidine is a disordered potassium feldspar.  It is similar in many ways to monocline but its appearance is more glassy.

Orthoclase and adularia are two types of potassium feldspar that are partially ordered.  Perthite is an intergrowth between two types:  microcline and anorthite.  Anorthoclase is sodium and potassium feldspar and it would have been perthite if it had not cooled so rapidly.  Celsian is a rare type of feldspar that contains barium.

 

 

weather

There is a light glaze over the cars, sidewalks, roads, and everything else.  Rumor had it that school was cancelled due to slipperiness but I'm not sure.  I have a couple of errands out in the shop but I am staying indoors until it's safe to walk.  I have a fear of fallling and breaking my arm again.  The other break never really healed.

I am sorting and dusting books and trying to put them in some order.  The science and rockhounding books will find a home out in the shop, for people to read and consult, and perhaps my collection will grow.  I have a lot of Einstein books.

 Next time I will blog about feldspar, the most abundant mineral in the earth's crust.

more about silicates

Amorphous silica is noncrystallline and deposited as a gel with water content.  The most obvious example is opal, which comes in many varieties.  Common opal, which is pale colored, precious opal with its play of color, and fire opal which is red or yellow, also with a play of color.  Opal wood is petrified wood with opal as the petrifying material.  Tripolite is opalized diatoms (small critters) which forms a powder used for polishing, and hyalite which is opal crusts on rocks.

Another example of amorphous silica is silica glass, formed when lightning strikes quartz (fulgarites) , or when quartz is struck by a meteorite.  It's quite rare  because the temperature required to melt quartz is quite high. 

Gem varieties of silica are opal and quartz crystals in various colors:  rock crystal, rose quartz, amethyst, smoky quartz, milky quartz and citrine.  Sagenitic quartz has inclusions such as rutiles (rutilated quartz) and quartz pseudomorphs are minerals in which the structure has been replaced by quartz.  An example is tigereye, in which the original asbestos fibers  are visible.

 Cristabolite is  the form of silica that remains stable at high temperatures.  Quartz turns to cristabolite at 1055 C and the change is permanent. Cristabolite is often seen in obsidian as the "snowflaek" pattern.  Similar to cristabolite is tridymite, also found in high temperature minerals.

frame silicates

The frame silicates are exciting for the average rockhound.  It is these minerals that brought a lot of people into the business/hobby.

The silica group of frame silicates includes free silica in large crystals, cryptocrystalline varieties (grains can only be seen in a microscope), and amorphous silica containing water.

Quartz is everywhere.  Its uses are many:  firebrick, gemstones, electronics, and it is the principal component of glass.  Most people are familiar with the hexagonal structure of a quartz crystal.  Cryptocrystalline quartz starts out as amorphous gel and the water settles out, leaving colorful banded and patternes materials that have been given separate names.

Chert is the duller, more opaque variety of cryptocrystalline quartz.  Jasper is one of its subcategories.  Jasper can be any color but is usually brightly colored and patterned.  Flint is a black variety of chert.  Aventurine is chert with mica particles that make is sparkly.  Cherts are useful for making stone tools such as arrowheads, due to their conchoidal fracture.

Chalcedony is the more translucent variety of cryptocrystalline quartz.  Gem varieties of onyx are agate, onyx, sardonyx, tigereye, carnelian and chrysoprase.

clay minerals

The clay minerals are commonly thought of as any rock or soil material consisting of small particles that can be molded when wet.  Technically, the term for them is  hydrous aluminium phillosylicates.  Clays are a major constituent of soils.  There are many groups, such as kaolinite, montmorillonite/smectite, Illlite and chlorite.  There are numerous subcategories, which is a subject unto itself. 

Uses for clay run into the thousands:  ceramics, fuller's earth, meerschaum, fire bricks, carbonless paper, bricks, tile, pottery, filtering, as a filler in plastics and rubber and so on.  

I remember an old Girl Scouts book I had  once that explained how to extract clay from soil, make it into useful objects, and fire it.   

 

 

mica group

The mica group of sheet silicates is kinda confusing.  There are two basic types, muscovite and biotite.  So here goes:

Muscovite is the commonest mica.  Only feldspar and quartz are more abundant in the earth's crust.  It is formed in granites and other silica-rich rocks, and in metamorphic rocks.  It is also a component of shales.  There is a chromium bearing muscovite called fuchsite that is attractive as a specimen.  

There are many more varieties of biotite than muscovite and many have been given separate names.  Biotites contain much iron and are found in igneous rocks, granites, gabbros, lavas and many metamorphic rocks.  Some of the varieties are haughtonite, siderophyllite, manganaophyllite, wodanite, titanobiotite, and calciobiotite.  

Phlogopite is essentially a biotite with more magnesium than iron.  It typically shows an asterism in transmitted.  Phlogopite too is divided into several varieties:  paragonite, margarite, prehnite, lepidolite, and glauconite.

 I am back in the deep freeze and the cats are back in the house.