I blogged about nitrates and adamite but it looks like the blog builder ate up my work.
Rocks In My Head
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
Talc is one of the more useful sheet silicates. It's used as talcum powder, in ceramics and for insulation. Soapstone and steatite are impure talc formations used as sinks and countertops in chemical labs. They are acid resistant.
Pyrophillite is almost identical to talc and looks quite a bit the same. It is more rare but has the same uses as talc. Pyrophillite has a structural relationship to mica. Both talc and pyrophillite are common in metamorphic areas such as New England.
I spent the past two or three days working on the computer and watching TV, MLK observances, the inauguration, and so on.
I can't seem to motivate myself when it's this cold. The weather man promised a warm up today but it was still 45 below according to my thermometer, which is always at least 10 degrees colder. Either the thermometer is wrong or I am in a pocket of cold. I use the computer in a heated porch but the windows on the south side leave a little to be desired so I go to bed early. The next subject to be considered is talc but I will leave that to another day.
Right now I'm going to fix a cup of hot carob. The day seems right to make soup. Somewhere I have a Tanzanian recipe and it is very very good. Calls for coconut milk which maybe isn't good for you but when I was on Blogit, one of my fellow bloggers indicated that despite the drawbacks of tropical oils, there is something in coconut that contributes to human health. Moderation is the key, I think.
The serpentine group of sheet silicates is called that because most of the examples have a green, patterned appearance. The recognized varieties are antigorite, lizardite, and chrysotile. It is very difficult to tell them apart without using x-ray and miscroscope equipment.
It is not known why the serpentine varieties differ in appearance. Reasons may be impurities, pressure and temperature when they were formed, minerals present, the water content, and so on.
Fibrous serpentine is used to make asbestos fabric and making fire brick.
Sheet silicates exhibit one directional cleavage. This is because the bonding between the sheets is weak. These minerals have a greasy feel and lubicating qualities. An example of weak bonding is mica,in which the sheets separate easily.
The kaolinite group includes kaolinite and three others with similar chemical composition but different structure. The other three are dickite (funny name) , nacrite, and halloysite. Kaolinite is important for use in pharmaceuticals, firebrick, china, and as a whitening agent.
I joined an online wire wrap group today. I wonder if I will learn anything.
The double chain silicates are formed so that many ionic substitutions are possible, therefore the chemical varieties are endless. All double chain silicates are in the amphibole group. These contain water and are formed at lower temperatures than olivines and pyroxenes. There are over thirty varieties. Some of the more well known are actinolite, of which nephrite jade is largely composed, and hornblende, found in basaltic lavas in mountainous areas of the world. Some very large rocks are mostly hornblende.
A bit warmer today. I may get back to the photographing of materials from Ely or whatever I can find.
Between being sick, and snowed in, I've barely let the house this month. Now I have to venture out and fill a rock order. Fortunately, my worst cold in years might be going the other way. On the dark side, it was thirty below this morning.
The next group of minerals to be considered are the single chain silicates, also known as pyroxenes. This group includes several well known gemstones.
Here are some of the single chain silicates: diopside, enstatite, hedbergite, aigote. ju[ersthene, aegerite, johannsenite, rhodonite, jadeite, wollastonite, spodumene, chrysocolla. How many do you recognize?Quite a few, I would imagine. This is a major group of rock forming minerals.