THE ROCK CYCLE
There are three main classes of rocks. They are classified according to how they originated. IGNEOUS rocks form from cooling bodies of magma. Over time, various weathering processes erode these rocks and the resulting particles or chemicals settle into beds and are compressed and cemented into SEDIMENTARY rocks. If these rocks are buried, heated and highly compressed they will be made into METAMORPHIC rocks. If these rocks continue to be heated and compressed to the point they melt, then the molten rock might eventually form another igneous rock. This is called the rock cycle. It forms a complete circle as one rock can be turned into another. They can even form differant rocks of their own class. A sedimentary rock such as sandstone can be weathered and eroded and those fragments might eventually end up as part of a shale, a different sedimentary rock
1. Agate: Hardness: 7 Agate is a microcrystalline variety of quartz, chiefly chalcedony, characterized by its fineness of grain and brightness of clor. Although agates may be found in various kinds of rock, they are classically associated with volcanic rock but can be common in certain metamorphic rocks. Agate is characterized for the most part by color bands in a concentric form, and less often by moss like inclusions. The characteristic bands usually follow the outline of the cavity in which the mineral has formed. The banded colors are determined by the differing impurities present, and occur in shades of white, yellow, gray, pale blue, brown, pink, red or black. Agates have been worked since prehistoric times, and were among the world’s first lapidary materials.
2. Amethyst: Hardness: 7 Amethyst is a purple quartz crystal. Its colr is from traces of iron. Amethyst may be found in light to dark shades of purple. It can be heated to change its color to citrine. When amethyst and citrine occur naturally in the same crystal it is called ametrine. The ancient Greeks believed that drinking wine from a cup made of amethyst would keep them from getting drunk. Amethyst is the February birthstone.
3. Apache tear: Hardness: 5-5.5 Apache tears are rounded obsidian. Obsidian forms when lava turns to solid so quickly that mineral crystals do not have time to grow. Iron and magnesium gives the obsidian a dark green to black color. The white matrix on the apache tear is pearlite. Obsidian was used by American Indians and many other ancient peoples to create weapons, tools, and ornaments. The Aztecs and the Greeks used it for mirrors because it is so reflective. Obsidian is an igneous rock. Obsidian has been used for blades in surgery, as well-crafted obsidian blades have a cutting edge many times sharper than high quality steel surgical scalpels.
4; Apatite: Hardness: 5 The name derived from the Greek apate, meaning "deceit" and referring to its similarity to crystals of other minerals such as auamarine, amethyst, and oviline, It can be intensely colored, occurring in green, blue, voilet-blue, purple, colorless, white, yellow, flesh, or rose-red forms. Apitie is an accessory mineral in a wide range of igneous rocks. It is also found in bedded marine deposits, which are frequently mined as a source of phosphorus. Apatite is an important source of phosphorus, used for matches. Moon rocks collected by astronauts during the Apollo program contain traces of apatite.
5. Aquamarine: (beryl) Hardness: 7.5-8 Aquamarine is almost universally found in cavities in pegmatites or in alluvial deposits (rivers/creeks), and form in large and clear crystals. One transparent crystal from Brazil weighed 245 pounds. In the nineteenth century, sea-green aquamarine was highly valued; today sky-blue crystals imparted by traces of iron are preferred. Traditionally aquamarine has been used as a charm by sailors for protection while at sea. Aquamarine is the March birthstone.
6. Aventurine: Hardness: 7 Aventurine is a variety of quartz that has a spangled apperance due to sparkling internal reflections from uniformly oriented minute inclusions of other minerals. Green aventurine is colored by green fuchsite mica. Other colors are brown, reddish-brown, orange, blueish-white, yellow, or blueish-green. Aventurine is used for jewelry, where it is cut en cabochon, for vases and bowls, and other ornamental objects.
7. Beryl: Few have ever heard of the mineral beryl, but almost everyone has heard of its principal gemstone varieties- emerald and aquamarine the most comon variety. Other gemstone varieties are helidor (golden yellow), morganite (pink), and goshenite (colorless). Common beryl ranges in color from tan to pale green, pale or sky-blue, or yellowish.
8. Calcite: Hardness: 3 (orange, red, green, honey, and blue) Calcite is the most common form of calcium carbonate and is known for the great variety and beautiful development of its crystals. Although it forms spectacular crystals, most calcite is massive, occurring either as limestone or marble. It is also found as fibers, nodules, stalactites, and as an earthy aggregate. It is found in many geological environments. In hydrothermal deposits, the habits of its crystals are good indicators of depositional temperature and other conditions. Calcite in general is so widespread that crystallized specimens are found in virtually every country. The largest documented single crystal of calcite originated from Iceland and weighed about 250 tons.
9. Carnelian: Hardness: 7 Carnelian a blood red to reddish-orange translucent variety of chalcedony. Its coloration is due to the presence of iron oxide, and it can be uniformly colored or banded. Strongly banded material is known as carnelian agate. Carnelian was once thought to still the blood and calm the temper. Conversely, it was also said to give the owner coverage in battle, and help timid speakers to be eloquent.
10. Chalcopyrite: Hardness: 3.5-4 Chalcopyrite, its name is derived from the Greek Khalkos, "copper" and "pyrite", chalcopyrite is a tetragonal mineral, usually forming crystals shaped like tetrahedral. On freshley broken surfaces, it is brassy yellow. Broken surfaces often form an iridescent tarnish. It is commonly found in hydrothermal ore veins deposited at medium and high tempatures, and as replacements, often associated with large concentrations of pyrite.
11. Citrine: Hardness: 7 Citrine is a yellow to brownish quartz and resembles topaz.It is colored by hydrous iron oxide. Natural citrine is much less comon than amethyst or smoky quartz, both of which can be heat-treated to turn their color into that of citrine. Citrine is said to give emotional control while making one more alert. Citrine can replace topaz for November's birthstone.
12. Emerald: (beryl) Hardness: 7.5-8 Emeralds green color results from trace chromium. It is found in grantic rocks and their associated pegmatite dikes, of mica schists, and of gneisses. To the Egyptians emeralds were a symble of fertility and life. The Aztecs called emerald quetzalitzli and associated it with the quetzal, a bird with long green feathers-a symbol of seasonal renewal. Emarald is the birthstone of May.
13. Fluorite: Hardness: 4 Fluorite has the widest color range of any mineral. It can be colorless, white, or various shades of purple, green, yellow, or rarely pink and red. Several colors can occur in the same piece. Violet, green, and yellow are the most common colors. It also often shows different fluorescent colors under ultraviolet light. Some pieces will omit light as they are heated. Fluorite occurs as a vein mineral, often associated with lead and silver ores; it occurs in pegmatite cavities, sedimentary rocks, and in hot-springs areas. The Romans particularly prized fluorite vessels (cups) because of the flavor given to the wine drunk from them. This flavor was actually the result of the resin used to help hold the crystals together during manufacture.
14. Fossil wood: Also known as petrified wood. A fossil is a remnant, impression, or trace of an organism that has lived in a past geological age. Some have been preserved in fine-grained sedimentary rocks, such as limestone and shale. The most common fossils found are of plant and animals that once lived in a sea or lake. Typically, after an organism dies. When trees fall in or near water and are buried by accumulating sedimates, minerals replace the cells of the wood and create fossil wood. Some can be subject to such a high degree of mineral replacement, literally cell by cell, that the detail of its original cell structure is preserved exactly.
15. Fuchsite: Hardness: 2.5 Fuchsite is the chromium-bearing variety of muscovite mica. The intensity of its color depends on chromium concentration, which may be up to 25 percent. It is found where hydrothermal solutions have replaced carbonates in gold deposits, and in metamorphic rocks corundum and staurolite schists.
16 Garnet: Hardness: 6.5-7.5 Garnets are a widespread mineral, particularly abundant in metamorphic rocks. There are 15 garnet species from colorless to black. There is an Arizona pyrope garnet that is called ant hill garnet, because ants bring up the smaller crystals from below ground and deposit them in the ant hill. During the 1800’s Navajos in Arizona used the water-worn and rounded ant hill garnet crystals as bullets. The use had a practical side (the stones were there and free) and they believed the blood-red color helped produce fatal wounds. Star garnets exhibit a property called chatoyancy. Chatoyancy is the reflection of light from microscopic inclusions of other minerals within the gemstone. A common cause of chatoyancy is the presence of the mineral rutile (titanium oxide). Garnet is the birthstone of January.
17. Geodes: Geodes are geological rock formations which occur in sedimentary and certain volcanic rocks. The exterior of the most common geodes is generally limestone or a related rock, while the interior contains quartz crystals and or chalcedony deposits. Other geodes are completely filled with crystal, being solid all the way through. These types of geodes are called nodules. Geodes can form in any cavity, but the term is usually reserved for more or less rounded formations in igneous and sedimentary rocks, while the more general term vug is applied to cavities in fissures and veins. They can form in gas bubbles in igneous rocks, such as vesicles in basaltic lavas, or as in the American south west, rounded cavities in sedimentary formations. After rock around the cavity hardens, dissolved silicates and or carbonates are deposited on the inside surface. Over time, this slow feed of mineral constituents from ground water or hydrothermal solutions allows crystals to form inside the hollow chamber. Most geodes contain clear quartz crystals, while others have purple amethyst crystals. Still others can have agate, chalcedony, or jasper banding or crystals such as calcite, dolomite, celesite, etc. There is no easy way of telling what the inside of a geode holds until it is cut open or broken apart. In 2000 a team of geologists found a cave filled with gypsum crystals in abandoned silver mine near Almeria, Spain. The cavity, which measures 1.8 x 1.7 meters, would be the largest geode ever found.
18. Girasol opal / Star Quartz: Hardness: 7 Star quartz is a colorless variety of star rose quartz. It may cotain needle like inclusions, which when polished may create a star effect in the stone. Girasol opal; I recently read an article on girasol opal. The suppliers out of Madagascar have misnamed this and have been selling it as girasol opal or blue opal. It is infact only a cloudy variety of quartz (white quartz or star white quartz).
19. Howlite: Hardness: 3.5 Howlite is a borate mineral found in evaporite deposits. The most common form of howlite is irregular nodules, sometimes resembling cauliflower. Crystals are rare. The nodules are white with fine grain gray and black veins of other minerals running through it, often in a web-like pattern. Because of its porous texture, howlite can be easily dyed to imitate other minerals, especially turquoise because of the superficial similarity of the veining patterns.
20. Iron pyrite: Hardness: 6-6.5 Pyrite occurs in many different shapes and forms, from massive aggregates to distinct crystals. It is also found in nodules and as attractive, coin shaped “suns” of radiating crystals. Pyrite is perhaps better known by its formal name “fools gold”. Its name is derived from the Greek word pyr, meaning “ fire “, because pyrite emits sparks when struck by iron, Native peoples of the American south west polished slices in to a wooden base to construct mirrors. Pyrite forms in contact metamorphic rocks, and in sedimentary rocks, such as shale, coal, and limestone.
21. Jasper: Hardness: 7 Jasper is a dense variety of cryptocrystalline quartz; it is a chalcedony incorporating various amounts of other minerals that give its opacity and color. Brick-red to brownish-red jasper contains hematite. Jasper forms in a numerous variety of other colors. It is formed through deposition from low-temperature, silica-rich waters percolating through cracks and fissures in other rocks, incorporating a variety of materials in the process. Jasperized fossil wood is found in Arizona. The Babylonians believed that jasper influenced women’s diseases, and was a symbol of childbirth.
22. Labradorite: Hardness: 6-6.5 Labradorite can be yellow, orange, red or green. It is commonly characterized by its “schiller” effect-a rich play of iridescent colors, principally blue, on cleavage surfaces. The schiller effect is caused by the scattering of light from thin layers of a second feldspar that develops through internal chemical separation during the cooling of what was originally a single feldspar
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23. Magnetite: Hardness: 5.5-6 Magnetite is magnetic. It will attract iron filings and deflect a compass needle. It is a high-temperature accessory mineral in igneous and metamorphic rocks. Magnetite is said to be named for the Greek shepherd boy Magnes, who noticed that the iron ferrule of his staff and the nails of his shoes clung to the magnetite-bearing rock.
24. Moonstone: Hardness: 6-6.5 Moonstone is an opalescent variety of orthoclase and some other feldspar, which has a blue or white sheen known as schiller. This sheen is a result of the inter layering of orthoclase with albite. It is abundant in igneous rocks, in pegmatites, and in gneisses. Moonstone was sacred in India, where it was said that if lovers placed it in their mouths during the full moon, their futures would be revealed.
25. Onyx: Hardness: 7 Onyx is a cryptocrystalline variety of quartz. It forms from the deposition of silica at low temperatures from silica-rich waters percolating through cracks and fissures in other rocks. Pure black onyx is common, and perhaps the most famous variety, but not as common as onyx with banded colors, the color of its bands range from white to almost every color. Commonly, specimens of onyx available contain bands of colors of white, tan, and brown.
26. Orange Millennium: Orange Millennium is a new find from Arizona. It was discovered in the 21st century (this millennium), which explains its name. It is small pieces of carnelian naturally glued together. Orange millennium is a sedimentary rock. Nick named dog food
27. Peridot: Hardness: 6.5-7 Peridot gets its color from small amounts of iron. It occurs commonly in mafic and ultra mafic igneous rocks. Peridot was considered a symbol of the sun from ancient time to the middle ages, and an early Greek manuscript informs us that it confers royal dignity on its bearer. To be protected from evil spirits, the owner of a peridot should have it pierced, strung on the hair of a donkey, and tied around the left arm- according to the 11th – century French bishop. Peridot is the birthstone of August.
28. Quartz / Rock crystal: Hardness: 7 Quartz / Rock crystal a colorless variety of quartz. It is silicon dioxide, the third most common mineral in earths crust after ice and feldspar. Quartz occurs in nearly all silica-rich metamorphic, sedimentary, and igneous rocks. Most of the sand on the beach is nothing more than tiny pieces of quartz. The Navajos believed it to be quartz crystal that first caused the sun to cast its light upon the world. Roman naturalist Pliny the Elder believed quartz to be permanently frozen ice. He supported this idea by saying quartz is found near glaciers in the Alps and that large quartz crystals were fashioned into spheres to cool the hands
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29. Rose Quartz: Hardness: 7 Rose quartz is rarely found in crystal, and when these occur, they seldom exceed a half inch (1 cm) in length. It is far more commonly found as massive aggregate. Rose quartz gets its pink coloring from the titanium within it. The nickname for rose quartz is pink ice.
30. Ruby: Hardness: 9 Ruby gets its coloration from traces of chromium. Next to diamond, ruby {corundum) is the hardest mineral on earth. It is most abundant in metamorphic rocks, and silica-deficient rocks. Rubies tend to be small (stones more than 10 carats are unusual), as the presence of chromium has an inhibiting effect on crystal growth-hence the high value of large rubies. According to the 11th century French bishop “ruby” is the solitary and glowing eye which dragons carry in the middle of their foreheads”. Russian popular tradition maintains that it is good for the heart, brain, vitality, and for clearing the blood. Ruby is the birthstone of July.
31. Rutilated Quartz: Hardness: 7 Rutilated quartz takes its name from needles of rutile that are enclosed within it. It is generally transparent, with any amount of needles from a few to so many that the stone may be nearly opaque. The needles can occur as sprays, or they can be randomly oriented. The rutile is generally golden, but it can be reddish to deep red, and appearing black without intense light.
32. Sapphire: Hardness: 9 Sapphire and ruby are, in fact, the same mineral-corundum, natural aluminum oxide. Red corundum is called ruby. When it is found in any other color, it is called sapphire. Next to diamond, corundum is the hardest mineral on earth. Corundum is found in a wide range of colors. It is most abundant in metamorphic rocks, and in silica-deficient igneous rocks. In ancient Greece, and later in the midle ages, there was a belief that sapphire cured eye diseases. Sapphire is the birthstone of September.
33. Selenite and Desert Rose: Hardness: 2 Selenite, from the greek word selen, meaning "the moon", it's the name for transparent crystals of gypsum. Rosette-shaped crystals are called desert roses, and are more common and less dense than the barite "sand crystals" that they resemble. Gypsum occurs in extensive beds formed by the evaporation of ocean brine. It has low solubility and so is the first mineral to seperate from sea water. The Romans discovered that heating gypsum to 600 degrees Fahrenheit made a plaster that sets hard when mixed with water. This plaster was used for building and is still widely used today.
34. Smoky Quartz: Hardness: 7 Smoky quartz is light brown to nearly black variety of quartz. Very dark, natural smoky quartz may be heated to give a lighter, more attractive color, and may turn it yellow. It may be found in large quantities of feldspar deposits.
35. Snow Flake Obsidian: The small white spots (flakes) are the mineral christobalite which occurs as white octahedra or spherullites in obsidian. See Apache tear above for more on obsidian.
35. Sodalite: Hardness: 5.5-6 Sodalite principally occurs in silica-poor igneous rocks. Crystals are relatively rare. It is sometimes in volcanic ejecta and in contact metamorphic limestone and domomites. The white in spotted sodalite is feldspar.
36. Tiger Eye: Hardness: 7 Tiger eye is a semiprecious variety of quartz exhibiting chatoyancy, a vertical luminescent band like that of a cat’s eye. Tiger eye is formed when parallel veins of crocidolite (blue asbestos) fibers are first altered to iron oxides and then replaced by silica. Tiger eye can be in blue and red, but it most common in yellow.
37. Topaz: Hardness: 8 Topaz is formed by fluorine-bearing vapors given off during the last stages of the crystallization of various igneous rocks, typically occurring in cavities in rhyolites, granites, pegmatite dikes, and hydrothermal veins. Topaz can be heated to change its color. In 1944 a 385-ton crystal was reported found in Brazil. Topaz is the birthstone of November.
FOSSILS
1. Ammonite: Fossil: The name comes from its appearance: It resembles a ram’s horn. In Egyptian mythology, the god Ammon looked like a man with horns, like a ram. The ancient fossil was considered Ammon’s stone, thus inheriting the name, ammonite. Ammonites first appear in the lower Devonian period (aprox.416 MYA). It is thought by some that they evolved from the older nautiloids. While little is known for sure about the life style of these extinct mollusks, we can make some educated guesses. Since all living cephalopods are predators we can assume that ammonites were as well. The ammonites as a class survived several mass extinctions during their long tenure among the living. However the end of the cretaceous period (aprox.65.5 MYA) was also the end for this class of cephalopods.
2. Brachiopod: Fossil: They are bottom dwelling, ocean, bivalves (having 2 shells). They are considered living fossils, with 3 orders present in today’s ocean. They are rare today but during the Paleozoic Era (542-251 MYA) they dominated the sea floors. Though they appear to be similar to clams or oysters they are not related. They are not even mollusks. They belong to the phylum lophophorata and are related to bryozoans. All members are filter feeders. They feast upon microscopic organisms and bits of organtic matter. Brachiopods have a long geologic history. They have been around since the Cambrian period (542-488.3 MYA). From the Ordovician period (488.3-443.7 MYA) through the Permian period (299-251 MYA). They were abundant. The Permian extinction reduced their numbers severely.
3. Coral: Fossil: Coral first appeared in the Ordovician period (488.3-443.7 MYA); corals are found mainly as tree like or tube like fossils. Through geologic time, corals have formed extensive limestone deposits and reefs. Two coral groups are extinct (Rogosa and Tabulata). Found in many shallow, warm-water seas, coral reefs provide evidence of highly diverse fossil fauna and flora. The bulk of a reef is a mass of cemented skeletons shell fragments of animals that once inhabited the reef. The Solnhofen limestone in Germany-which during the Jurassic period (199.6-145.5 MYA) was an extensive coral reef with lagoons-has provided geologists with evidence of more than 450 species of Jurassic animals.
4. Crinoids: Fossil: Also known as Sea Lilies, crinoids are a group of echinoderms that usually posses a cup-shaped body and five or more feathery arms. They attach themselves to the sea bed by a flexible stem made up of disliked plates that are either circular or pentagonal in cross section. Crinoid fossils are most often found as segments of stems and arms, and as disarticulated cup-plates. Complete crinoids are rare and beautiful fossils. They first appeared during early Ordovician period (488.7-443.7 MYA) and are still living today. During the Paleozoic Era (542-251 MYA), they became very abundant. In fact, the Mississippian Period (359-318) has long been known as the “Age of Crinoids”. Vast colonies of crinoids lived in shallow seas during this time, and their remains built up beds of limestone hundreds of feet thick.
5. Orthoceras: Fossil: Orthoceras was an ancient mollusk that lived more than 400 million years ago. The name means straight horn, referring to the characteristic long, straight, conical shell. The preserved shell is all that remains of this ancestor of our modern-day squid. These straight shelled nautiloids ranged in size from less than a centimeter to more than 14 feet long. All the living relatives of these nautiloids, squid, octopus, cuttlefish, and nautilus are predators, and we can assume that orthoceras was also a hunter of the Paleozoic seas (542-251 MYA), possibly having trilobites for breakfast.
6. Sea Urchin: Fossil: Commonly called sea urchin and sand dollar, they are infact echinoids, they are a group of echinoderms with a rigid, globular skeleton made of thin calcite plates. Many possessed spines, also made of calcite, attached to the body by a ball-and-socket arrangement. The spines were used for defense and, in some cases, walking. Some echinoids were bottom-feeders, foraging on the sea bed; others tend to burrow into soft silt layers and lived by filter-feeding organic material from the mud. They appeared in the cretaceous period. (144 MYA) Today’s spiny sea urchin is a living relative of species now known only from fossils.
7. Fossil Shark, stingray, Fish, Reptile Teeth and Bones are from Morocco and are aprox.
45-70 Million Years Old.
MYA = million years ago
