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.