How to Work Black Coral

by coralnut on January 1, 2009

OK, OK, Gail has asked for a copy of my tome on working with black coral.  Please understand this is an edited and somewhat shorter version of my Lapidary Journal article of Aug 2000 but it has been updated with new information and provides all the basic procedures to successfully work with this material.  Once again I want to emphasize: BLACK CORAL OF ALL GENRE IS HIGHLY PROTECTED BY INTERNATIONAL TREATY AND IT IS ILLEGAL TO REMOVE IT FROM ITS NATURAL HABITAT WITHOUT PROPER LICENSE OR PURPOSE.  ALL BLACK CORAL USED BY THIS AUTHOR HAS BEEN HARVESTED BY MOTHER NATURE AND IS CASUALLY COLLECTED FROM BEACHES.  IF YOU WISH TO WORK WITH IT, PLEASE RESPECT THE LAW!

How to Collect and Process Black Coral

By Donald C. Dietz (An excerpt from his August 2000 Lapidary Journal article)


            Florida’s Gorgonian black coral species most suitable for making jewelry are the sea bush  (pseudoplexaura parosa [porous false plexaura]), knobby or spiny candelabrum (eunicea species), tan bushy coral (plexaura flexuosa), common bushy coral (plexaura homomalla), and Guadeloupe sea blade ( pterogorgia guadalupensis). Other species such as sea fans, sea rods, sea plumes, sea feathers and deadman’s fingers, can also be found but are either not black when dried or otherwise have more limited use for jewelry purposes.  A few words are in order regarding sea feathers and sea plumes, often grouped with “black coral”. These varieties are not easy to clean due to the tough spines running the length of the long graceful stems.  They can be smoothed, with some effort, and take a beautiful polish which shows them to be dark brown to nearly black in cross section but very dark brown with lighter brown twisted lateral bundles in the axial view.  Cross sections of a large diameter limb can make excellent cabochons but I have found no easy method to bend or shape the brittle (and tough) stems other than slow heating.  Straight polished segments make beautiful hair pins, etc. I have also found that the main stems from both of these corals and deadman’s fingers coral can be used to make beautiful beads.


            Additionally, the true “sea fans” (gorgonia ventalina and gorgonia flabellum) as found in South Florida are rare and highly protected and usually either too small or too fragile for making jewelry, though they may make excellent specimens.


            Often black coral is freshly blown onto South Florida’s beaches with little or no damage and with the calcareous outer shell (spicules) still clinging to the limbs. Black coral can be found caught in the rocks of breakwaters, tangled with seaweed or fishing lines at the water line or just lying on the beach. A sharp eye can often spot the top two to three inches of a coral branch sticking out of the sand.  The reward may be a large buried branch or tree. 


            When found wet on the beach, the surface of black coral, sans the spicules, will appear muddy brown.  But do not be misled because as it dries the layers compact, actually shrinking by a quarter or more in size and turn jet black.  Actually, black coral isn’t black.  It is a bit like “black” nephrite jade; i.e., a piece of thin nephrite held up to a light looks green or brown; whereas the coral appears brownish red.                                  


            Occasionally a coral tree with the spicules still attached may be found saturated with black oil.  Wait until it dries and then break off the outer layer by pounding it gently with a wooden mallet or blunt object such as the edge of a board then wash with Gunk.


            When collecting fresh black coral, you may notice a strong fishy odor due to saltwater saturating the coral skeleton and any remaining calcareous layer, or seaweed clinging to the branches.  Clean the coral of debris before leaving the beach and rinse it with fresh water at a beach shower before putting it in your car.  Rinse again at home with fresh water and dry it in the afternoon sun.  By then the smell will be sufficiently lessened that it can be taken indoors to dry completely for two to three weeks.


             It is important to pick up the coral as soon as possible after it is deposited on the beach because the hot sand “cooks” it and makes it brittle.  Also the coral will begin to deteriorate and display brown “woody” spots.  Eventually the entire tree will turn brown. This is difficult to remove and can result in loss of valuable material, though at times, small spots create lovely patterns that may be incorporated into a jewelry design.  Remember, the larger and blacker the coral, the more beautiful it is, and the easier it is to clean and work into various designs.




            The physical properties of black coral generally support its usefulness as a jewelry material, but some also work against it.  One attribute is its workability with the simplest of tools.  It can be trimmed, smoothed and polished much in the same manner as a fine hard wood.  It is ultra-light and when polished to a high shine feels and looks much like black plastic.  Small or thin pieces may be quite brittle but thick material is quite durable.  The polish must be protected from abrasion or it will become dull sometimes taking a beautiful patina.  It chars easily when subjected to an open flame and the surface will “burn” and turn light brown due to friction when polished on a felt wheel.  Thin wet limbs are easily bent or formed into many shapes and even tied into knots. When dry, it is stiff and hard and takes an excellent polish, however, after being formed to a particular shape it must be protected from water, which it will absorb making it soft and pliable again.  Thus, beautiful hoop earrings could at best become horseshoe-shaped, or at worst a long shapeless stick.


            I have collected bits and pieces of black coral for many years and have seen it fashioned as jewelry in parts of Japan and on Hawaii where it is revered as a gift of nature by native Hawaiians.  But, while practicing the art of lapidary and gold and silversmithing for over 35 years, I never learned how to work with it until the article “Black Coral Pendant” by June Culp Zeitner appeared in the Jewelry Journal of the March 1996 Lapidary Journal.  This article spurred my interest and after researching Lapidary Journal articles dating from the 1960’s, and various other references, I was hooked.  Now I actively search the beaches hoping to find that one gigantic black coral tree.  Meanwhile, I will settle for any little piece that looks like I can get an earring or perhaps a small pendant out of it.




            Anyone with rudimentary lapidary, woodworking, or crafting experience can learn to work with black coral.  The necessary tools will vary with ones’ talents and preference but will generally consist of small saws, various files, knives, several grades of sandpaper, polish compounds, a polishing motor and buffs, drills and various wheels, and other items that can be used to smooth, shape, bend and polish.                                                                                                                                                                                                                                                                           

            First look at the raw dry coral with its twisted and gnarled limbs, uneven surfaces, and tree like appearance for a hint of something unusual.  Look for a particularly shaped crotch formed where one limb grows from another, or several off-shoots that might form a geometric (or un-geometric) design.  Is a branch long and well shaped with few or no offshoots?  Is it about the same size from where it leaves the main trunk to its end?  Are the trunks and branches round, thick, and smooth or flattened with irregularities?  If you do not have a specific design in mind these shapes may influence what you can or should do.  If you have something specific to make, find the material that will fit your plan.  Plan how to cut the tree keeping the pieces you consider usable and discarding the rest, though I find it difficult to throw any of it away unless a piece is badly deteriorated, too thin or heavily infested with disease.  The latter is indicated by hollows or bubbles in the surface of the trunk and is filled with a form of calcium carbonate.  Take a good look at the ends of the long branches.  If hollow, they cannot be easily bent or shaped without kinking except in long graceful curves.  The best coral is solid except for a tiny core usually about the diameter of a pinpoint. Look at the main trunk and limbs, which should also be solid and jet-black.  If there are woody or calcareous areas growing into or under the surface, or hollows, you must decide to remove them or keep them as they are.


            Cut and trim the coral into pieces that are the size or shape necessary to do a project.  Use a hacksaw, jewelers saw, various cut off blades in a Dremel or Foredom tool, a small scroll saw or whatever you find convenient to cut through a piece of dry coral up to an inch thick.  Small limbs can be snipped with side cutters but this leaves a ragged stub that must be filed down.  The goal is cut the coral tree into pieces of varying size and shape that can be smoothed, formed, and polished.  I find a 360-degree scroll saw blade very useful for getting into tight areas.  Fine cutting can be done with a jeweler’s blade or small back cut saw.  Motorized cut-off blades are quick and leave a neat cut but cause a lot of dust and, if used at high speed, can burn the coral.  When using any motorized blade or tool, wear a dust filter mask and eye protection.  The make up of gorgonius is protein with high concentrations of iodine and bromine but there is no telling what other chemicals or minerals are present.  In any event, I doubt if the dust is good for your health and some people are allergic to it. Always wash any exposed skin immediately after working with black coral.


            I have read articles that discuss the sanding or “grinding” of black coral when it is wet.  I have tried it and, for me at least, it does not work. It appears that the wet process may be limited to the Antipatharian or deep-water variety of black coral that comes mostly from Hawaii but can also be found in some parts of the Caribbean.  It is slightly harder and more stone like than the shallow water Gorgonian found in Florida waters.    Other than soaking the coral in preparation for bending or forming of branches, the following steps are all performed on bone dry coral.  


        If you are working slender branches with offshoots, it will be nearly impossible to clean and polish in the crotches.  Thus, it is important to open them up sufficiently to have access with smoothing tools and polishing wheels.  Do this by holding the area in front of a heat gun (1500 watt hair dryers work to some extend but a heat gun is much better) for a few seconds and then gently open the crotch.  This can also be used to straighten bent areas.  Let the coral rest a minute or so and it will retain is new shape. It can always be reshaped by reheating and bending.

 Remove nubs along the limbs by filing or sanding before generally smoothing any damaged areas.  I use a heavy-duty half round wax rasp to remove large surface blemishes followed by finer files to smooth and shape the surface.  Try to retain the natural curves or surface grain, but otherwise the surface must be even and smooth enough to get at it with a buffing wheel. Sometimes the grain is so clear and nicely formed it is wise not to polish it. The initial smoothing is a difficult step because it requires considerable hand strength to hold the coral steady while filing or cutting.  Also, you may find coral difficult to smooth when filing in one direction due to growth grain, which may change several times throughout the length of a branch.  Merely change the direction of your smoothing stroke to accommodate the grain. There is no one file or method that is best at this stage.  Large pieces may be easier to manipulate but might require more filing or cutting. Small or thin pieces are more difficult to hold but may be naturally smooth.  The process is much like cutting a stone–each succeeding step shapes and smoothes the material so that scratch lines from the previous step are removed. As you smooth the surface, blemishes may appear.  Especially troublesome are the holes that result from removing off-shoot branches. Sometimes the core-hole extends into the middle of the mother branch, while other times it is very shallow. Nothing can be done about the former except to cut them out, while the latter can be filed out resulting in a longer more useful stem.


            After filing, I have found various types of nail files/sponges to be useful.  These can be purchased in most department or drug stores.  I normally start with one that is an inch wide by 8 inches long with180- or 240-grit silicon carbide on a hard but flexible board.  This does an excellent job on larger pieces and easily takes out the file marks.  Some minor shaping can also be done but the general shape should already have been determined by cutting/filing.  Next I use an acrylic nail file that has a 280-grit on one side and 320- or 400-grit on the other with a foam board in the middle.  This board is softer and follows the rounded contours well.  It also gives a nearly ready to polish surface.  Hard to get places can be cleaned and smoothed using various plastic scouring/sanding pads.  These are excellent for getting into crotches and between limbs.  Final sanding can be done with worn 400- or 600-grit silicon carbide paper.  These final smoothing steps are important because they take the work out of polishing. 


            Any remaining scratches must either be re-smoothed or polished away using considerable pressure against the polishing wheel, which could result in overheating the surface and burning the coral. When this occurs, it is nearly impossible to remove the resulting brown area.  Brown speckles (caused by deterioration) that remain after final sanding can sometimes be removed by scraping across the surface with a very sharp hobby knife or a razor blade.  This removes material more quickly than filing or sanding, and leaves the surface relatively smooth. With practice, you can control exactly where and how much material is removed.


            I have found it best to polish coral before forming, bending, or making the final piece of jewelry.  Forming and bending may result in curves or corners that are difficult to access for smoothing and polishing. Even after soaking and forming the coral, about 80 to 90% of the pre-polish will remain.  If you intend to carve the piece, it is wise to pre-polish as it can reveal imperfections or an irregular shape that could affect your plans.  At this stage these can often be corrected.   


            ZAM is an excellent overall polish for black coral. Fabuluster, black emery, rouge, and some others do a good pre-polish but finishing with ZAM seems to give the highest luster.  Whatever polish you use, use it on a multi-layered, one inch wide sewn muslin cotton buffing wheel.  Do not use felt; the high surface temperature will quickly burn your coral.  A 3450-RPM motor is recommended but a 1725-RPM or just about any other motor can be used in a pinch including a flex-shaft.  If the buffing wheel becomes too hard cut the stitches to soften it.  This will ensure the polishing compound penetrates the wheel and gives good polishing action.  Use smaller 1-1/2” to 2” inch diameter cotton wheels on your Dremel or Foredom tool for the hard to get places but be careful as these wheels may “burn” the surface or grab the piece from your hand.


            There are some tricks to getting a good polish on black coral.  Keep the wheel well loaded with polish.  Initially, keep the piece horizontal to the wheel and support it with your fingers or a wood block.  Run it back and forth the length of the coral branch, using moderate to heavy pressure.  This will quickly highlight any remaining filing, sanding marks or irregularities. Under the proper speed, pressure and polishing medium the outer layers of protein melt and flow.  Thus, minor scratches or surface blemishes may polish out.  Otherwise, correct them by additional sanding before continuing.  After you are satisfied all such marks are removed and the coral has an even shiny appearance, run the coral lengthwise (vertically) up and down the wheel parallel to the grain using light pressure.  The resulting shine will be well worth all the effort you have put into preparing your coral.




            Shaping black coral is an experience in itself.  Thick solid pieces can be carved or sanded to any shape.  Keep in mind the center (or slightly off-center) core can suddenly appear right in the middle of your otherwise beautifully carved humped-back whale.  Be aware also of any hollows or other blemishes previously identified or suspected.  Start with easy shapes; an easy one to make looks like a baseball bat.  You may also incorporate any original curve into the new form.  More sophisticated bends or curves can be attained by soaking the polished black coral branch in water (hot water does it faster; cold a bit slower but just as effective) and forming it around a dowel, or inside various items such as a jar lid or a can. In the past few years, I have used the heat gun mentioned above, to bend large diameter pieces for necklaces/bangles or to readjust/tighten designs such as knots and braids. While learning to work with black coral, select only solid pieces, as you will find the hollow ones difficult to work with. As you gain experience, you will find the hollow limbs useful in some forms as well. Following are some examples to obtain specific shapes. 


            To make large hoops, place two wet branches 4 to 10mm in diameter inside a jar or can with a 2 inch inside diameter.  If you want the ends to meet when dry, overlap them by about 1/2 inch.  To create a hoop with a 1/4 to 1/2 inch gap make the ends meet when wet; they will separate as they dry. If the branch has some irregularities in its length, wait until it is just about dry, remove it from the jar/can and place a flat weight of about 4 to 8 ounces on it for 12 hours.  This will insure it is a flat round hoop. Adjustments can be made with the heat gun.


            To make several other shapes, drill a hole in the end of a 1/2 to 3/4 inch wood dowel, insert one end of a wet 4 to 6mm x 6 inch branch and wrap it around.  Tape, nail, or pin it at the ends to keep it from unwinding.  Let it dry for at least 24 hours and slide it off of the dowel. Cut the tightly wound coil lengthwise to make small hoops (as in making jump rings).  Dampen the hoops slightly and dry under a 4 to 8 oz weight to bring the ends even or adjust with the heat gun. 

            To stretch the tightly wound coral into a corkscrew, slightly dampen or heat it, pull the ends apart until it is the shape you desire and let it dry/cool. A simple crossed loop can be made by bending a wet branch around a 1/4 inch dowel and pinning the coral at the point where they cross.  Let it dry for 24 hours.


            Many other shapes can be obtained by the use of clips, dowels, jars, cans, boards with pins or holes in them or special “jigs” designed to hold the coral in a specific position until it has completely dried. If a shape does not quite conform to your specifications, dampen or heat it and try again.


             Use steam from a tea kettle to quickly form or correct bends and curves.  A propane torch, alcohol lamp, “lil torch”, or heat gun can be used to gently heat the coral for forming.  Heat should be used only as one becomes more experienced as the coral can easily burn or become misshapen.  The secret is to not be in a hurry.  Give the coral plenty of time to set-up and dry or cool otherwise it may become warped.  When wet, thin branches of solid coral can even be tied into various kinds of attractive knots, provided they are not pulled too tight too quickly.




            After the black coral has been shaped, it can be drilled with a variety of twist drills or points to fit sterling silver or gold findings. Eye pins or other findings can be glued into the coral with epoxy.  The ends of hoop ear rings or bracelets can be finished by making a small bezel cup, adding a jump ring and attaching the cup to the coral with epoxy. There is almost no end to the variety of designs for black coral.  It looks just as beautiful with gold or silver; add pearls, red or pink coral beads, or gemstones to achieve your concept. Stones such as turquoise or opal are beautiful when inlayed and framed by the jet black and shiny coral.  (Hint:  When drilling, do not push the drill in too quickly as it will expand, graband subsequently break the drill. Instead insert it in short quick strokes.  This cleans the hole and allows the coral to cool slightly).



(Edited 1 Jan 2009)






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{ 5 comments… read them below or add one }

payday loans February 13, 2010 at 10:41 pm

I am completely impressed with the article I have just read. I wish the author of can continue to provide so much worthwhile information and unforgettable experience to readers. There is not much to tell except the following universal truth: The converse of UT 405 is not always true I will be back.

Larry E. Whittington January 2, 2009 at 10:55 pm

When I purchased one ladies lapidary materials, I found several small boxes containing one or two small pieces of black coral. Most seem to be already cleaned and polished I want to use these short pieces in some jewelry in the future. I don’t know how to price the pieces of coral since there was no prices marked on the boxes. Where can I go for some suggested prices for something like these.

Jane Walker January 2, 2009 at 10:35 pm

Thanks, Don! I’m happily eyeing my little stash and figuring just how much easier it is going to be to work with this extra knowledge.

Gail Rappa January 2, 2009 at 9:33 pm

Thanks so much Don! talk soon- GAIL

Hans Meevis January 2, 2009 at 11:10 am

Thanks Don,
Even though you sent me these notes a while ago, it is great to read the expert advice of a maestro again. Thank you.

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