Herkimer Diamonds

These are not true diamonds, but they have their own beauty. Herkimer “Diamonds” are naturally double-terminated (also called “double point) quartz crystals that can have amazing clarity (truly crystal clear). Each crystal is a six-sided prism terminated at both ends by a rhombohedron: thereby making 18 crystal faces (facets). When the terminations are equally developed, the appearance is that of a hexagonal dipyramid. 

Herkimer “Diamonds” are unlike diamonds in that the former are natural and do not require cutting and smoothing by humans. Herkimer “Diamonds” have a hardness of 7 on the Mohs Scale (note: all quartz has a hardness of 7); thus they are not as hard as true diamonds, which have a hardness of 10.

Herkimer “Diamonds” are found at and near Herkimer, Herkimer County, New York, about a 4.5- hour drive west from New York City. These crystals occur in the very fine-grained, gray-colored Little Falls Dolostone of Cambrian age (500 million years old). Dolostone is a combination of dolomite and limestone, and dolostone fizzes weakly in a 10% solution of hydrochloric acid.

The Herkimer “Diamond” crystals always occur in vugs (cavities, like those associated with geodes) within the dolostone, and the precipitation of these crystals probably took place during the Carboniferous age, about 300 million years ago. The Herkimer “Diamond” crystals need air space. Without the “air space,” they cannot form doubly terminated crystals. They do not adhere to the dolostone. They can adhere, however, to each other, but only at the end points of the crystals. Thus, they weather out of the outcrop as individual crystals. Their value depends on the their size and how clear (translucent) they are. Some of the crystals have inclusions (small fragments of impurities), which are most commonly pieces of black hydrocarbon material.

Shown below, is a tiny Herkimer “Diamond” quartz crystal (5.5 mm long and 2.5 mm wide) still inside a tiny vug in the Little Falls Dolostone. 

Below, a larger Herkimer “Diamond” crystal (22 mm long and 9 mm wide) is shown. This crystal is not perfectly clear. It has some incipient milky quartz cloudiness, which comes from microscopic inclusions of fluids stemming from when the crystal grew. This specimen also has some black hydrocarbon inclusions.

If you are ever in the vicinity of Herkimer County, you might want to stop and do your own collecting (for a fee). It is not every day one finds doubly terminated quartz crystals that are so perfectly clear.

REMARKABLE SLUMP-FOLDED BEDS

This post concerns an “eye-popping” section of extremely slump-folded sandstone beds within the Chatsworth Formation, in the Simi Hills of Ventura County, southern California. You have to see the actual beds, or see a picture of them, in order to believe it.

These slump-folds are of Late Cretaceous age (late Campanian/early Maastrichtian age, about 70 million years old). They are located on protected land.

Three images of these slump beds are shown below (a person provides the scale): the first two are essentially the same view, but the second of these two was taken under different lighting. The third image is of the same channelized flow but a several meters westward, near the lowermost part of the slump feature.

The folded/crumpled beds consist of numerous wedge-outs of sand-rich deposits (with a sandstone to mudstone ratio of 12:1). These beds filled a braided-channel, turbidite deposit in a deep-sea-fan system of a submarine middle-fan environment (see references below for all the gory details). Turbidites are deposits of sediment-gravity flows which include turbidity currents, fluidized sediment flow, grain flow, and debris-flow mechanisms. The beds were originally in a semi-liquid state, unstable, and slid down a slope.

For more details, see the following references:

Link, M.H. 1981. Sand-rich turbidite facies of the Upper Cretaceous Chatsworth Formation, Simi Hills, California. Pp. 63–70, in Link, M.H., R.L. Squires, and I.P. Colburn, (eds). Simi Hills Cretaceous turbidites, southern California. Pacific Section, Society of Economic Paleontology and Mineralogy [Guidebook]. Los Angeles, California. 134 pp.

Note:  This slump fold was illustrated also on the cover of AAPG, v. 67, no. 3, 1983.

Link, M.H., I.P. Colburn, and R.L. Squires. 1984. Slope and deep-sea fan facies and paleogeography of Upper Cretaceous Chatsworth Formation, Simi Hills, California. The American Association of Petroleum Geologists, v. 68 (no. 7):850-873, 22 figs., 4 tables. Note: See Fig. 12D for a picture of the slump fold illustrated in this present blog post. 

How And When Did Monkeys Get To South America?

Monkeys live today in the Old World (Africa and Asia) and in the New World (South America, Central America, and southern Mexico). The consensus has been that they originated in Africa, but it is not known with certainty how they managed to get to South America. You might think that the answer is they that they simply walked from Africa to South America, but the answer is not that straightforward. 

Here are the paleontologic facts: 

The earliest known fossils of monkeys are found in Africa (Egypt) and in South America (Bolivia and in the Amazon region of Peru). They are all about the same geologic age: latest Eocene/early Oligocene (about 33-35 million years ago). The problem is that there was 1,400 km of open ocean between Africa and South America at that time (and previously for a long time—millions of years earlier, during Cretaceous time).

So, that nagging question is: “how did monkeys get from Africa to South America.” The usual answer, which that has been around since the 1960s and is still in vogue today, is that African monkeys floated on clumps of forest vegetation (e.g., modestly large forested islets) that floated downriver and eventually ended up in the ocean. These clumps then drifted across the Atlantic Ocean to South America during late Eocene/early Oligocene time. The shortest distance would have would been 1,400 km, and the drifting is estimated to have taken at least 60 days. Then monkeys then would have had to transverse overland a long distance, from the eastern shores of South America, in order to reach the inland jungles of Bolivia. This widely believed “floating-vegetation theory” is commonly referred to as the “accidental transoceanic dispersal” theory. 

Another theory is that the earliest monkeys reached South America via southern North America during late Eocene time. This theory, as well as the one discussed above, are questionably indicated on the following known paleogeographic map that shows the position of South America, relative to North America and Africa during the late Eocene. The few scientists who advocate this second theory of a dispersal route via North America have proposed, furthermore, that monkeys originated even earlier that late Eocene time. For example, in Wyoming, a sparse record of early Eocene fossils that resemble marmosets (= New World monkeys) is known.

 

While you contemplate the unsolved mystery of the ancient geographic dispersal of monkeys, it is useful to give you some background biologic information to consider. Monkey are primates. Primates include the prosmians (lemurs, bush babies, lories, pottos, and tarsiers) and also the anthropoids (monkeys, gibbons, apes, and humans). Old World monkeys consist of several families, and these are referred to as the catarrhines. They are characterized by having nostrils separated by only a thin partition, and they also have jaws with two premolars. Two examples of catarrhines are the macque monkey and baboons. Old World monkeys do not have prehensile tails. Old World monkeys include both arboreal (live in trees) and ground-dwellers.

An example of a modern-day catarrhine monkey (from Japan) is shown above. Photo credit: Wikipedia, 2021.

The New World (South America, Central America, and southern Mexico) monkeys are referred to as the platyrrhines. They are characterized by having nostrils that are quite separate, and they also have jaws with three premolars. Two examples of platyrrhines are shown here: cebids and marmussets New World monkeys have a grasping prehensile tails. New World monkeys are only arboreal.

An example of a modern-day platyrrhine monkey (cebid) from Costa Rica. Photo credit: Wikipedia, 2021.

A second example of another modern-day platyrrhine monkey (marmoset). Photo credit: Wikipedia, 2021.

A relatively recently published comparative study of mitochondrial genes of primates has been interpreted as agreeing with the fossil data showing that platyrrhines split from catarrhines at around 35 million years ago. The authors of the mitochrondrial study also advocated the “floating on vegetation” theory (see discussion above).

USEFUL REFERENCE;

For an excellent article concerning evolution of mammals in South America, I highly recommend: https://dcpaleo.org/south-americna-fossil-mammals/

TERROR BIRDS

The generalized term “terror birds” is the focus of this post. It refers to a group of extinct similar looking birds that could be up to 8 or 10 feet tall and weighing 400 pounds. There were several genera/species, and they make up an extinct group of carnivorous flightless birds, referred to as the phorusrhacids. They were the largest apex predators to live in South America during the Cenozoic Era.

One example of this group is genus Phorusrhacos [pronounced For-us-Rah-koss], of middle Miocene age, about 14 million years ago, from Santa Cruz, southern Argentina. Although it superficially resembles an ostrich, it is not one. The skull of Phorusrhacos is very different. Phorusrhacos was 8 feet tall and weight 300 pounds or more. A model of this genus is shown below. 

The geologic time range of “terror birds” is most of the Cenozoic, from late early Paleocene, late Danian Stage [=62 million years], through the early Pleistocene [=1.8 million years]; an interval of approximately 60 million years. Why did they go extinct? Most likely, it was because of changing habitat (related to changing climate during the Pleistocene Ice Age). Also the Panamanian Land Bridge emerged during the Pleistocene, and South America became connected to North America, and large predatory cats and dogs migrated southward into South America for the first time.

It is interesting to mention that the geologically youngest “terror bird” (Titanis walleri = 8 feet tall and 300 pounds), of early Pliocene to early Pleistocene, lived in Texas and Florida. This shows that at least a “terror birds” migrated northward into North America, but their presence there did not last long.

The geologic history of birds, in general, is a complex subject. They originated during the “time of dinosaurs” during the Jurassic Period, but their diversity increased significantly during Cenozoic time. A very generalized cartoon showing the major different groups of Cenozoic birds is shown below. The “story” of bird evolution is still unfolding.  

I encourage you to “Google” the words “terror birds” or Phorusrhacos. There are MANY online colorful renditions of what this animal and its relatives looked like. 

Wild Turkeys Once Lived in Southern California

 This post is appropriately “published” just prior to Thanksgiving Day, 2021 and gives a nod to the turkey, a bird native to North America. 

The earliest known fossils of turkeys are of early Miocene age (23 million years old). They are from near the small town of Bell, northern Florida in northern Gilchrist County, approximately 30 miles northwest of Gainesville. These fossils belong to the extinct genus Rhegminornis, which was about half the size of the modern genus Meleagris, whose type species is M. galiopavo (also known as the wild turkey). The latter is the largest gallinaceous bird (refers to its order in the classification system of birds) in the New World. It is 3-4 feet tall, 10-40 pounds in weight, and has a wingspan up to 6 feet. These turkeys are very social animals, yet territorial.

Today, M. galiopavo lives in the forests of midwestern and eastern United States and into southeastern Canada. I can verify a Gulf Coast occurrence because I saw a wild turkey in southern Alabama, while I was on a fossil-collecting trip (gastropods and bivalves) many years ago. I can also confirm that this species can fly. The one I saw flew high into a tree top. This wild species is the ancestor of the domestic turkey.

A second living species, M. ocellata, lives in the forests of the Yucatán Peninsula, Mexico.

Another species of Meleagris is the extinct Meleagris californica, which lived in southern California during the Pleistocene Ice Age. Bones of this species represent the second most common fossil found in the Rancho La Brea Tar Pits. The most common fossil is the Golden Eagle. Meleagris californica went extinct about 10,000 years ago.

For more detailed information, I highly recommend that you Google rexmachinablog.com for its excellent blog on “The Wild Turkey: the evolution and history of an American icon.”

If you are interested in detailed information about the Rancho La Brea turkeys, see the following pdf (downloadable, for free):

Bockénski, Z.M. and K.E. Campbell, Jr. 2006. The extinct California turkey, Meleagris californica, from Rancho La Brea: comparative osteology and systematics. Contributions in Science, number 509, 92 pp. Natural History Musem of Los Angeles County, California.

The Silica Tetrahedron

The molecular structure of silica tetrahedron (SiO₄) is the basic building block of the silicate minerals, which make up the vast majority of the minerals in the Earth’s crust.

The silica tetrahedron is a combination of one silicon and four oxygen atoms that form a four-sided pyramid shape, with the silicon atom in the center and an oxygen at each corner of the pyramid.

This low-tech "marshmallow model"shows the basic design of the silicon tetrahedron.

In a more explicit model of a silica tetrahedron (see below), the element silicon is a cation with a charge of +4. Each oxygen atom is an anion, with a -2 charge; thus four oxygen atoms make a -8 charge. The combination of +4 and -8 makes -4. The silicon tetrahedron molecule has therefore has a net -4 charge, which means it readily combines with other elements besides oxygen in order to balance out the additional -4 negative charge and form a net-zero charge (i.e., nature abhors a molecule with a net negative charge; just like nature “abhors a vacuum”).

There are six main configurations (e.g., rings, chains, frameworks etc.) of linkage among silicon tetrahedra. There are many internet sites that show beautiful reconstructions of these configurations, some of which are quite complicated. One of the most useful sites is: <openeduationalberta.ca/practicalgeology/chapter 3>  You will have to access it yourself because Google no longer allows external links within blogs.

The mineral quartz (SiO₂), which is the most abundant mineral in the Earth’s crust is an  example of the framework configuration known as the tectosilicates. In quartz, in order to neutralize the ionic charge difference, the four oxygen atoms of the silica tetrahedron are “shared” by adjacent silica tetrahedra. Each corner of the pyramidal tetrahedron is bonded to another tetrahedra (with an oxygen shared at each corner of each). As a result, the ratio of silica to oxygen atoms is 1:2, and the atomic charge is neutral (zero). 

A cluster of clear quartz crystals (6.5 cm wide, 6 cm high).

A single crystal of clear quartz (2.4 cm wide, 5.7 cm high).

One of the simplest silicate minerals is olivine, which is made up a single tetrahedron bonded to divalent iron (+2) and/or magnesium (+2), thereby creating Fe₂SiO4 or Mg₂SiO4, or some combination of the two (Fe, Mg)₂SiO4. The combination can occur because both iron and magnesium are divalent (+2) [thus they balance the charge of the silica tetrahedron] and their atomic sizes are similar; thus they can substitute for one another.

The above image is a cluster of tiny olivine crystals (hand specimen 3.6 cm wide, 2.7 cm high).

Terminology Hints

The words silicon and silica, etc., get used a lot in our modern vocabulary. The following list might be of some help to you in understanding these similar terms:

silicon (Si) = the 14^th element on the “Periodic Table of The Elements.”

silica = a solid material made out of SiO₂ (but not necessarily a mineral; e.g., opal---see my previous post on chalcedony).

silica tetrahedron = a combination of one silicon atom and four oxygen atoms that form a tetrahedron (= a four-sided pyramidal shape).

silicate = a mineral that contains a silica tetrahedron or many silica tetrahedra. 

silicone = a flexible synthethic material made up of Si-O chains with added organic molecules.

SMITHSONITE: the blue-green variety

Smithsonite was named in honor of James Smith, founder of the Smithsonian Institution.

This mineral belongs to the carbonate group and consists of zinc carbonate ZnCO3. It effervesces in hydrochloric acid. Its streak is white, and it has silky luster, its specific gravity is 4.4–4.5, its hardness is 4.5. Its crystals belong to the trigonal system, but they are rare. Smithsonite commonly occurs in either a globular (botryoidal) or in a massive (granular) form. 

It has a wide range of colors because of chemical impurities (listed here in brackets): white to gray [no impurities]; blue, blue-green, to apple green [copper]; yellow [cadmium]; pink to purple [cobalt]; and brown to red [iron].

It often forms as a secondary mineral in the upper oxidation zone of zinc-ore deposits within metamorphic rock complexes. It is found in Greece, Spain, Africa, and the USA (one famous example is at the Kelly Mine in New Mexico).

The two images shown above are of the botryoidal form of an encrustation of smithsonite (38 mm length an 9 mm in height) from the Kelly Mine at Magadalena, Socorro County, central New Mexico.

 

Whale Shark

The modern-day whale shark Rhinocodon typus (family Rhinocodontidae) is dark gray in color with white spots and stripes. Its body has a very wide and squarish head (up to 5 feet wide) with many (about 300), rather small, single-cusped teeth. The whale shark is commonly referred to as a whale because of its large size, but Rhinocodon typus is a shark, not a whale. A whale is a mammal, and the whale shark is a giant filter- feeding elasmobranch (shark = a fish). The whale shark is the largest known shark today, thus it is the  largest known living fish. It can up to about 40 feet in length. The first three images show the left side, top, and front (mouth) views of a model of R. typus.

The whale shark is a slow-moving fish that is found globally today, except in the Mediterranean Sea. It likes tropical waters, and is known to seasonally congregate in the following areas: California to Chile, especially in the Gulf of California (=”Sea of Cortez”) in Baja California (Mexico); Yucutan (Mexico); Belize; Western Australia (especially lagoons and coral atolls) to Japan; Maldives Island (Indian Ocean); and New York to central Brazil.

Whale sharks feed on microscopic zooplankton (copepods) and, to a lesser degree, on small fish, fish eggs, and small squids. They are filter feeders: they have modified pads (gill rakers) along their gills and can screen the water for food as it moves through the gills. For their larger prey, they use suction feeding (sucking in large quantities of water containing the food). Whale sharks are harmless to humans. Their teeth are small.  

 

As shown in the diagram above, the earliest known “whale” sharks lived approximately 56 million years old (late Paleocene or early Eocene in age) and belong to the genus Palaeorhinodon. Their teeth, which are small and single cusped, have been found in Africa, central Asia, Europe, and eastern North America (e.g., South Carolina and Virginia). Their geographic distribution coincides with the ancient Tethys Sea, which stretched from Java and India and westward through southern Europe. These warm waters affected, as well, the east coast of the United States. To my knowledge, they did not live along the west coast of the United States during this time even though the climate was warm there. 

Also, as shown in the diagram above, the first known whale shark belonging to genus Rhinocodon appeared during the middle Oligocene, about 28 million years ago. Their teeth, which are also small and single cusped, have been found along the east coast of North America, where warm warms lingered. They did not occur along the west coast of the United States because of continued climate cooling in this area. The fossil record of Rhinocodon ranges from the middle Oligocene to modern times.

In the modern oceans, in addition to whale sharks, there are two other similar looking, giant filter-feeding elasomobranchs: megamouth sharks, and basking sharks. Their geologic time ranges are younger than that for whale sharks (see diagram below).

Megamouth (family Megachasmidae, genus/species Megachasma pelagios) is another large shark that eats plankton. This shark ranges from the late Oligocene/early Miocene, about 23 million years ago, to today. Recent individuals can reach 12–15 feet long. This fish was

unknown to science until 1976, when a specimen was found entangled in a parachute anchor of a U.S. oceanographic vessel off of Oahu, Hawaii. This shark is named for its enormously distensible mouth and protrusible jaws containing overly 100 rows of small hooked teeth. It has a poorly calcified skeleton, therefore, it is a weak swimmer. A drawing of it is shown below:

Furthermore, “Megachasma pelagios was discovered in 1976 off the coast of the Hawaiian Islands. The specimen shown below is the second megamouth ever found. It was caught by commercial fishermen in 1984 near Catalina Island, southern California. it is a 14.7-foot make, weighing approximately 1,540 pounds. In 1990, a live megamouth shark was caught off the coast of Dana Point, southern California. It was fitted with sonic transmitters and released. The transmitters revealed that the shark spends most of its time well below the surface, spending the night 50 feet below the surface, diving to 490 feet at dawn, and returing to shallower waters at dusk. Many marine animals display this vertical migration pattern as they follow plankton in the water.” (From signs displayed at the megamouth exhibit at the Los Angeles County Museum of Natural History, 2021). A head shot of this actual specimen is shown below:

The basking shark genus/species Cetorhinus maximus) is shown below. It is the world’s second largest fish (36 feet long). Like the whale shark and megamouth, the basking shark is a surface-feeder that eats plankton. It prefers temperate waters and shuns polar and equatorial waters. The geologic range of C. maximus is middle Miocene (15 million years ago) to today.

 

 

BIOMINERAL VS. MINERAL

 According to mineralogy textbooks, a mineral is a solid INORGANIC substance of natural occurrence. That definition rules out human-made simulants (e.g., cubic zirconia and nearly all mossanite --- see one of my recent previous posts). That definition also rules out organic substances secreted by organisms, even though these organic compounds have the same (or nearly same) chemical composition as “true” minerals. What to do? The answer is to use the terms biomineral, organic mineral, or biogenic mineral when dealing with organically secreted shells, teeth, bones, kidney stones, etc.

All five kingdoms and 55 phyla of organisms contain members that create biominerals. At last count, there are at least 60 known biominerals, but new ones are being discovered all the time. Most (80%) are crystalline, and some (20%) are amorphous. Many of these biominerals can be in the following groups (with examples given below): carbonates (calcite, aragonite), phosphates (dahllite, francolite), sulfates (gypsum, barite), silica (opal), iron-oxides (magnetite, goethite, ferrihydrite), iron sulfides (pyrite), halides (fluorite), and oxalates (weddelite).

Three comparisons of a biomineral versus its mineral counterpart are given below: 

FIRST COMPARISON: The biomineral that makes up vertebrate (including humans) bones and teeth is called dahllite [= hydroxylapatite (or also spelled hydroxyapatite)] consisting of Ca5(PO4)3(OH), which is = 45% calcium-rich phosphate, 33% organic matrix material (mainly collagen), and 22% water.

The following image is of an Eocene mammal tooth (5.3 cm length) consisting of generally well preserved dahllite:

The mineral apatite Ca5(PO4)3(F, Cl, OH) is an inorganic substance consisting of calcium phosphate combined, in varying amounts, with fluorine, chlorine, and hydroxyl ions. The mineral apatite, furthermore, is an end member of the complex apatite group, or series, of minerals with varying amounts of F, Cl, and OH. The mineral apatite has been long been known as a calcium-phosphate series of minerals found in igneous rocks (especially in hydrothermal veins) and in phosphate-rich sedimentary rocks. In summary, the biomineral dahllite [= hydroxylapatite] and the mineral apatite are chemically quite similar, and the difference is based on the content of the elements fluorine and/or chlorine, which are both subject to variation depending on the surrounding environment.

The following image is of a crystal (2 cm height) of inorganic apatite, with a hardness of 5 on the “Moh’s Scale of Hardness” (0 to 10, with 10 being the hardest = diamond).

 

SECOND COMPARSION: The biomineral aragonite (calcium carbonate [CaCO3 + organic matrix material]) versus the mineral aragonite (calcium carbonate [CaCO3]). Biomineral aragonite, common in some invertebrates, especially certain gastropods, bivalves, and, cephalopods (nautiloids and ammonites) can have iridescent “mother-of-pearl” luster, which I have mentioned in several of my previous posts. This luster indicates that there has been no alteration of the original composition of the shell material. The mineral aragonite never has iridescent luster, as is obvious in the image below of inorganic aragonite.

The following image is of the inside of a modern-day abalone shell (18.7 cm long) showing its “mother-of-pearl” biomineral aragonite luster. See my previous post July 28, 2020 for more details.

The next image is of the interior of a modern-day Nautilus shell (16 cm wide) showing its “mother-of-pearl” biomineral aragonite luster. See my previous post August 1, 2016 for more details.

The next image is of radiating crystal clusters of two specimens of aragonite of inorganic origin. Small cluster 2 cm wide, larger cluster 4 cm long. Impurities cause the reddish color.

THIRD COMPARISON: The biomineral opal (SiO2-xH2O) versus the mineral opal (SiO2-xH2O). Biomineral opal (transparent) is present in the test [microscopic shell] of single-cell, micro-organisms like diatoms [plant kingdom] and radiolarians [animal kingdom], as well as in glass sponges. The mineral opal, which can have an amazing array of colors but not transparency, is present in some sedimentary deposits.

The following two images are of the biomineral (opal), which forms the tests of a modern-day, microscopic radiolarians from deep-ocean sediment.

                                          single radiolarian

                             six more examples of radiolarians

The following image is of the biomineral (opal), which forms the exoskeleton (21 cm long) of Euplectella, a modern-day glass sponge. See my March 15, 2020 post for more details.

The last image is of a fragment (1 cm) of the mineral (opal) of precious opal. See my post Dec. 14, 2018 for more details.

The Elegant Lavender Interior of the Gastropod Drupa forum

The gastropod Drupa Röding, 1798 is a Pleistocene to Recent genus, with about eight species and several possible subspecies. The type species [the original species used to define this genus] is Drupa morum Röding, 1798, commonly known as the “Purple Drupa, the Purple Pacific Drupa, or the Mulberry drupe snail.” The word “drupa” is Latin for ripen, in the sense of ripening of fruit. The Drupa shell does resemble a small berry (e.g., Mulberry).

 

Drupa morum Röding, 1798 from the Indo-Pacific area. The first image above is of the dorsal (back) side of the shell. The second image is of the ventral (front) side of the shell. The characteristic lavender color of this species is on present on one side of the aperture. The number "2" at the top refers to a later slide, which shows this same specimen in a series of other specimens.

Genus Drupa belongs to family Muricidae, and some specialists place the genus in the subfamily Thaidinae. Drupa is a predatory gastropod that prefers to eat worms, as well as some gastropods. The modern-day geographic distribution of Drupa is essentially restricted to between 35°N and 35°S (the area in "red," shown in the map below), in the Indo-Pacific (tropical) shallow-marine waters among coral reefs or rocky areas. Many of the species of Drupa are widespread within this region.

The species of Drupa are determined by several main morphologic features: the number of spiral rows of knobs on the last whorl (largest whorl), the shape of the knobs, the number and position of the labral teeth on the outer lip, the number and position of the columellar teeth along one side of the aperture (the main opening of the shell), and the color of the aperture. The labral teeth and the columellar teeth (both the oblique and straight ones) are labelled on the immediately following image.

The next two "strip images" show a growth series of six specimens of D. morum. The first one shows the dorsal side of each shell (numbered in increasing size), and the following strip shows the corresponding ventral side of each shell.

 Height range is 27.3 to 35 mm.

If you look carefully, you will see that the number of labral teeth and the number of columellar teeth, as well as their spacing, are not all the same on every specimen, even though the sizes of the specimens are similar. Nevertheless, all six specimens are Drupa morum. If the identification were based on only two specimens (numbers 1 and 6---see image below), however, it would seem that there are two species. That is why one needs to study as many specimens as possible. The outer lip of D. morum is especially prone to reabsorption of the calcium carbonate making up the shell, thus the details of the outer lip are not constant.

In the following image, specimen no.1 had reabsorbed some of the shell material making up its labral teeth along the outer lip of its shell. Specimen no. 6, which has all of its labral teeth, is shown for comparison.

Turquoise, an exquisite blue/green gemstone

 The word “turquoise” is an old French adjective, used to describe objects taken from the region of Turkey. One of these objects includes beautiful sky blue to green stones, which were originally mined in the Sinai Peninsula or over 5,000 years, thereby making turquoise one of the first gemstones to be mined. 

Today, turquoise is most commonly found in the southwestern United States, Mexico, China, Chile, Egypt, and Iran.  

Turquoise is a hydrated copper aluminum phosphate mineral. Its chemical composition is CuAl6(PO4)4(OH08)-4H20. Its composition can be variable, and even turquoise deposits in the same general area can have slightly different chemical compositions.

It is a secondary mineral that forms in arid or semi-arid regions, when rainfall leaches copper, aluminum, and phosphorus out of host rocks (plutonic and volcanic igneous rocks, or sedimentary phosphate beds). The leached material can also include impurities (strontium, lead, etc.). When the requisite elements are in the right combination, they get re-precipitated as nodules, encrustations, in veins, or in massive form. 

Two views of a nugget (5 cm width) of turquoise with “spiderweb” cracks:

Lastly, a view of a thin crust (2.5 cm length) of turquoise:  

At certain locales in the southwestern United States, turquoise can be found as the result of weathering of hydrothermal porphyry-copper deposits (PCDs). For more information about PCDs, see my previous Post.

Also, in the southwestern United States, turquoise typically forms within 100 feet of the ground surface. The shallow depth allowed Indigeous Americans to mine mineral in areas now known as Arizona and New Mexico.