Kuphus giant bivalve tube

Many years ago, while in a shell shop, I came across a large calcareous (calcium-carbonate) tube, about the size of a baseball bat. Although this tube resembled a giant "worm" tube, it is a tube made by an extant giant teredinid ("shipworm") bivalve that once lived in on the bottom of a muddy mangrove in tropical waters, most likely in the vicinity of the Philippine Islands.

The scientific name of this giant bivalve is Kuphus polythalamus (Linnaeus, 1767). It was originally by Linnaeus as Serpula polythalamia, but this name was later updated to Kuphus polythalmus. Yet, the incorrect spelling of the species name of Kuphus polythalamia is still used currently by many workers.



This first image shows the tube in question. This tube is 33 1/4 in. in length (the yardstick shown here is in inches).  The largest reported tube of K. polythalamus is 61 inches (155 cm) in length and 2.4 inches (6 cm) in diameter.

This image shows a closeup of the exterior of the tube near one of its ends, which is 2 in. in diameter.  


The life position of K. polythalamus is vertical  and with a tiny "Y" at its posterior end. Most of the calcareous tube is encased by the mud. At the anterior end of the tube (i.e., the widest part of the tube), there is a thin calcareous cap that covers the mouth of the bivalve. This cap must be resorbed periodically to allow the animal to grow. The cap had been removed by the time I got the specimen shown above. 

The maximum known size of Kuphus polythalamus is 155 cm (61 in. = about 5 feet) in length and 6 cm (2.4 in.)  in diameter. Thus, this bivalve is the largest known bivalve in the world. It lives in black, organic-rich muds (i.e., stinky) in mangroves/shallow bays in tropical and subtropical oceans in the Philippines, Indonesia, and Mozambique. This bivalve uses bacteria in its gills to convert hydrogen sulfide in the muds/water into nutrients. 

The top image above is a view somewhat downward into the tube and showing the incomplete posterior end of the shell I have. You can see the two holes for the siphons, side by side; one for intake of water, and the other for expelling water. Their fleshy ends would have extended into the water column above the calcareous tube. The branching part of the "Y" is at the narrowest part of the tube, where the two fleshy siphons stick out a short distance from the two holes, which as shown in the top image, are situated near the end of the tube, but within it. These siphons bring in water into the gills of the bivalve, and they can also expel water. 

The bottom image above is a view into down the anterior end of the tube, next to the mouth. A temporary cap at this wider end is missing. This end of the bivalve is stuck down into the mud during life. 

This giant bivalve is a member of the common wood-boring and wood-feeding bivalve family Teredinidae, which are among the least studied extant bivalves. Until recently, the biology of Kuphus polythalamus was very poorly known. You can now go online and watch a video all about this animal. Just type in the incorrect scientific name.

Kuphus has a fossil record of a few species, some of which are known from Oligocene/Miocene beds.

If you go online, you can watch a dissection of a K. polythalamus. It is taken from research by Distel et al. (2017). There is also a free pdf available for downloading.  

Diamonds

This post is the second part of a "two-parter." See my previous post on graphite, which is an allotrope of diamond. An allotrope is each of two or more different physical forms in which an element can exist. Graphite, diamond, and charcoal are all allotropes of carbon. 

Like graphite, diamond is a native mineral. That means it consists of one element, which is carbon, with a chemical formula of C. Diamonds are measured in terms of carats, which refers to a diamond's weight, not its size. One carat = 200 milligrams = 0.200 grams = 1/5 of a gram. The "largest" diamond known is the "Golden Jubilee" (5,000 grams).

Most  diamonds are Precambrian in age (between 3.5 to 1 billion years old). They are formed at high temperature and pressure deep in the Earth's mantle, mostly between 150 to 250 km (93 to 155 miles) depth. Some however come from as deep as 500 miles. They can be carried to the Earth's surface by volcanic eruptions and occur mostly in the plugged-up necks of ancient volcanoes, in rocks known as kimberlites. If the kimberlites become exposed at the surface of the Earth, they become eroded and the diamonds can be concentrated in stream or beach deposits. One of most famous diamond localities is from South Africa, where diamonds have been weathered out from kimberlites and concentrated as placer or "lag material" in beaches.

Diamonds (very small size) have also been found in some meteorites. 

Diamond is the hardest naturally occurring substance, having a rating of 10 on the Mohs Hardness Scale (0 to 10). The arrangement of  the atoms in diamonds is classified under the isometric crystal system, and the resulting structure is extremely rigid. Many diamonds are pure, and as a result they are transparent and colorless. Others can have color, caused usually by the presence of minute impurities. The range of colors (with increasing rarity), along with the known impurity or other factors causing the color, are as follows: yellow (nitrogen), brown (defects), blue (boron), green (radiation exposure), black (referred to as "Carbonado"), gray, pink, orange, purple, and red (most rare of all diamonds).

A diamond, or a simulant? It is 3.5 mm in diameter.

The image above shows a round, "brilliant cut" of what is probably a simulant (synthetic) and not diamond. I found it in a parking lot, and I spotted it about 20 feet away from me, because of its extremely bright and very eye-catching display of reflected light. Part of its mounting was still attached and consisted of hardened copper.

I spent considerable time and effort in trying to determine if what I found is truly a diamond, or if it is a simulant (synthetic or "fake"). 
I tried all the "easy" tests [e.g., water, fog, scratch, newsprint], all of which have been shown as videos on the internet, to determine what I found, but the tests were not conclusive for my mystery "stone." 

There are several types of simulants (note: they are much less expensive that diamonds). Two of the most common ones are moissanite (silicon carbide) and cubic zirconia (zirconium dioxide). 

Moissanite is a very rare naturally occurring mineral, but most of it that is used to make jewelry is created synthetically in a lab. It has a hardness of 9.5, colorless and has more brilliance (flash-of-light, or "fire") than diamond. It is one of the best substitutes for diamond.

Cubic zirconia is an entirely lab-created substance. It has a hardness of 8 to 8.5, and it can scratch easily.  

Based on the fantastic brilliance in natural light of my mystery stone, as well as on the copper mount, I believed that it is probably moissanite and not a diamond. As I viewed numerous websites about diamonds and simulants, I discovered that some simulants can look really good. I discovered eventually that the best and most definitive way to distinguish between a cut diamond and the various simulants is to consult a gemologist or a reputable jeweler. Using a very precise machine, they will weight the material in question and compare it with a comparable-sized diamond. This kind determination will be reliable.

Graphite

This post consists of two parts. The first part is about graphite and the second part is about diamonds.

Graphite and diamond are native element (ones that consists of a single element). Like graphite, diamonds consist of pure carbon. These two natural forms of the element carbon (C) have the greatest contrast in structure and properties to be found in any pair of polymorphous substances.

Graphite has its atoms arranged in a hexagonal structure, which forms sheets that are poorly connected, thereby allowing the sheets to easily slide over one another if subjected to a small amount of force. Thus, graphite is slippery and greasy. That is why it is used in pencils (as in "lead" pencils) and also is used as a lubricant. Graphite is, furthermore, light, extremely soft, inert, and highly resistant to chemical changes. Graphite is a good conductor or heat and electricity and is used for making solar panels, batteries, and electrodes.

                       Specimen of graphite (3.2 cm from bottom to top of image).

Graphite forms predominantly in rocks affected by regional or contact metamorphism, and it is found in crystalline limestone, metamorphosed coal beds, schist, gneiss, quartzite. Locally, it can form in veins (pegmatites). Under high pressure and temperature, graphite converts to diamond. Graphite has been found also as minute crystals in some meteorites. 

Bowen's Reaction Series

Igneous rocks (e.g., granites, lava flows) are those created by the cooling of molten material called magma. As the magma cools, volatiles are lost, early formed minerals crystallize out and react with the remaining magma, and changes (either in a continuous fashion or a discontinuous one) in composition take place. This is called fractional crystallization. There is a sequence as to which minerals form first, second, third, and so on. This process is known as the Bowen's Reaction Series.

Note: The poster shown below depicts this process. I made it many years ago to help my students visualize the crystallization sequence. It was not made with the intention of showing it online. This explains why the the writing on the poster is a little hard to read, because I had to stand way back with my camera in order to photograph all the writing. Although the dark minerals do not show up very well, this poster is, nevertheless, useful because it conveys the main concept of the progressive sequence of crystallization of an ideal magma as it cools. It is especially helpful because I used actual minerals instead of just their names. 

The Bowen's Reaction Series is the result of research in the 1920's and 1930's by Norman Bowen, who was able to explain why certain types of minerals tend to found together (e.g., olivine and labradorite--see one of my earlier posts on labradorite) whereas others are almost never associated with one another (e.g., olivine and quartz). He experimented with powdered rock material that was heated until it melted and then allowed to cool to a target temperature, whereupon he observed the types of minerals that formed in the rocks produced. He repeated the process with progressively cooler temperatures, and the results allowed him to formulate his reaction series. His work showed that a geologist can infer, from the minerals present in a rock, the relative conditions under which the magma had formed.

The Bowen's Reaction Series can be combined also with crystal size and texture of the rock to determine whether the rock formed under the Earth's surface (plutonic igneous rocks with large crystals visible to the eye) or on the surface (volcanic igneous rocks with microscopic crystals). The rock names (e.g., peridotite, gabbro, granite) are indicated on the left side of the poster.

The following comments are intended only for individuals who are really interested in the details of the Bowen's Reaction Series.

The Bowen's Reaction Series consists of two main branches, the discontinuous reaction series (depicted on the left side of the poster: olivine, augite, hornblende, and biotite) and the continuous reaction series (depicted on the right side: anorthite, bytownite, labradorite, andesine, oligoclase, and albite). The last minerals (especially quartz) are generally considered to be the residual phases. Temperature cools as crystallization proceeds, with the high-temperature minerals forming first, and the low-temperature forming last. The word "continuous" refers to the continuous, series of solid solutions that are produced during the cooling. The word "discontinuous" refers to the ferro-magnesium minerals (e.g., augite) that form during the cooling process. They react with the melt and abruptly produce a new mineral, with different crystal structure and considerably different composition than the mineral that preceded them.

For the Bowen's Reaction Series to work in the perfect "flow chart" fashion (as shown on the poster) requires a magma with an ideal chemical composition and a long time for cooling. In reality, which minerals form are dictated largely by the chemical composition of the original molten material. Also, the Bowen's Reaction Series only goes to completion if there is enough time for the reactions to take place and enough Na, Al, and Si in the remaining melt to form each successive mineral. In the ideal situation, eventually only SiO2 (mineral quartz) is all that remains.

As the temperature (and pressure) decrease, a progression of feldspar minerals takes place. The plagioclase feldspars (anorthite, bytownite, labradorite, andesine, oligoclase, and albite), which have the formula (Ca, Na)(Al, Si)3O8, represent a single mineral (plagioclase) consisting of a solid-solution series with varying amounts of calcium (Ca) and sodium (Na). The highest temperature plagioclase (anorthite) has the highest calcium content. The lowest temperature plagioclase (albite) has the highest sodium content. In between, these ions mix in a continuous series with the calcium/sodium ratio varying from 100% Ca and 0% Na, to just the opposite.  This variable chemical composition creates the different colors of plagioclase. 

The cooler temperature alkali feldspars have varying amounts of potassium (K) and sodium (Na), and the ratio of these two elements also changes as the crystallization process proceeds. There are several of these minerals (anorthosite, microcline, sanidine, and orthoclase). Only orthoclase (KAlSi3 O8)is shown on the poster. 

The high-temperature minerals (e.g. anorthite, bytownite, labradorite) are the most unstable at the Earth's surface and quickest to weather because the Earth's surface is most different from the conditions which they were created. On the other hand, the low-temperature minerals (e.g., muscovite and quartz) are much more stable because the conditions at the surface are much more similar to the conditions under which they formed.

"Keyhole Limpets"

This post accompanies my previous one about “Shells with a Selenizone.” This new post, however, focuses on gastropod shells with only a single natural perforation (hole), rather than a spiral band of them.

Gastropod shells with only a single natural hole belong to family Fissurellidae (common name of this family is “keyhole limpets"). They have flattened, oval shells with an excurrent opening on their dorsal (top) surface. Their early stages have a spiral shell, but as the shell grows, the spiral shell is lost. Three examples of fissurellids are shown below. All three live attached to rocky surfaces, just like their selenizone-bearing relatives, the abalones.

 Megathura crenulata Sowerby. This shell is 7.5 cm long, but some individuals can secrete shells up to 15 cm long. During life, the shell is covered mostly by a fleshy mantle. The shell is radially striated, with a large, nearly central perforation. This gastropod lives in the low tide to subtidal depths on rock surfaces in the cool-coastal waters from Monterey Bay, California to central Baja California. The animal attaches itself to rocks. The common name of this gastropod is the “Giant Keyhole Limpet.”

Diodora aspersa. This shell is 5.5 cm long and is from the intertidal zone on the Olympic Peninsula, Washington State. The common name of this shell is “Rough Keyhole Limpet.” The shell is heavy, elevated, and has rough, coarse, radial ribs. This species ranges from Alaska to northern Baja California, Mexico. It is most abundant in the northern part of its range, where individuals can reach a size of 7 cm.

Fisssurella nodosa. This shell is 2.3 cm long and is from the West Indies. It is like other Fissurella shells in having an elevated conical shell, but the fleshy animal is unable to retract within the shell. Its natural opening in the shell is definitely keyhole-shaped. Fissurella gastropods are intertidal species that live primarily only in tropical waters. There is only one species found in the cool waters of California.