Tuesday, February 12, 2013

Coal or Jet? The Black Rocks from the Ocean...what are they???

Many people over the last few months have been given a beach combers treat...finding large black somewhat shiny rocks on the beach and or in the water.  Most think because of its look and weight that it is COAL , however an interesting thing happens to Coal when it is left for thousands of years it progresses its way to a density of hardness known as Jet and becomes shiny, and valuable as a gemstone.

  Jet was the only true black stone available during the time Queen Victoria went into mourning for her mother and husband who both passed in 1861.  Protocol was that widows wore black for a certain period , and all who felt her pain at that time chose to mourn with her...hence the Victorian Period.

You can tell coal from jet, one by the look Jet is a shiny black where as Coal is more of a matte finish. more like a seaglass smooth.  The large piece of Coal I have would have been Jet in another 1000 years or so as it is already showing some spots of shinieness.  Please see the pictures..

This is how to tell coal from Jet....
 You can take a small piece  of your find and light a match and put it to it, Coal  will ignite whereas Jet  will extinguish the flame of the match.

Coal takes thousands of years to form as it is a biochemical formation or sedimentary rock.  Organic Matter accumulates along the edges of seas, rivers and lakes and the process of flooding and non-flooding the plant matter is covered by water , soil and sand.  The water usually saline in nature prevents the decay of the matter and it will start the process of metamorphosis from plants to coal and eventually jet, and if the jet is left alone it will eventually under the right circumstances turn to a diamond the hardest known "rock" on earth.

Black jet usually has a shine, while coal is usually more of a solid black.
The degree of processing results in differing qualities of coal:

The following information came from this site.... it is a breakdown of the different stages of Plant Matter to coal to Jet.


PEAT - is not actually a rock yet, but no longer just organic matter, either. Peat is a major source of energy for many non-industrialized people of the world. The not-quite-consolidated plant matter is a precursor of true coals which is what it would have become had the material been left buried for a few million years more.

LIGNITE (or brown coal) -  is the least mature of the true coals and the most impure. It provides the least yield of energy of the true coals and burns the dirtiest. It is often crumbly, relatively moist and powdery.

SUB-BITUMINOUS - is still poorly indurated and brownish in color, but more like bituminous than lignite.

BITUMINOUS - is the coal most people are used to. The black, soft, slick rock is the most common coal used around the world.

ANTHRACITE - is usually considered to be the highest grade of coal and is actually considered to be metamorphic. Compared to other coals it is much harder, has a glassy luster, and is denser and blacker with few impurities. It is largely used for heating domestically as it burns with little smoke.

GRAPHITE - is essentially pure carbon and would actually be a higher grade of coal than anthracite, but is difficult to ignite and is rarely used for this purpose. Graphite forms from intense metamorphism and even igneous processing.

JET - is the gem variety of coal. Generally derived from anthracite, jet is where the phrase "jet black" comes from. Because it lacks a crystalline structure, jet is sometimes treated asa mineraloid.


For More cool information about Coal ...check out this link:


Coal (almost Jet another 1000 years) and Jet 


Almost Jet

A Close up of the almost jet...so basically it is Coal....

(′jet ¦kōl) (geology) A hard, lustrous, pure black variety of lignite, occurring in isolated masses in bituminous shale; thought to be derived from waterlogged driftwood. Also known as black amber.

Read more: http://www.answers.com/topic/jet-coal#ixzz2KjYkQJze

Well I hope you find this informative as much as I enjoyed finding out more than I already knew.


  1. pumpellyite - from the gold coast of australia or other volcanic regions. fulgurite man

  2. I have a large piece I found by the ocean beach I would love to know where I can find out either it's jet or coal

  3. Replies
    1. May I ask where in Maine? I believe I found some in Kittery

    2. Brittany I am not sure as I am only familiar with the ocean beaches of North Carolina. But there is enough info here to determine what you find is. Happy hunting

  4. I found almost jet in North Carolina this yr.

  5. Just found a piece in Hampton Va doing beach clean up.

  6. I found some in Galveston, Texas!

    1. Me too. Found all different stages of it too!

  7. I Just found some Jet in Hampton New Hampshire! On Mothers day!! What a gift! :)

  8. I found jet in rockawaybeach in NY two days ago