Sorry for being stubborn, but jet is not anthracite, nor another
sort of coal nor lignite. For a good explanation, see:
Nice page, though one should note that the owners/authors of that
page would have a distinct interest in distinguishing Jet from coal.
If you spend a bit of time browsing through the various Wikipedia
entries for coal types, as well as geologic periods, etc, several
things become clear. For one, there are many types and subtypes of
coal. All are fossilized forms of one or another type of organic
material, from bog,peat bog materials, to woods, And other such
material, compressed over time. The various types of coal differ
greatly in things like carbon content, water content, geologic age,
and characteristics like color, apparent structure (like wood, for
example), value as fuel, etc.
The descriptions given for Jet in your page pretty closely match
those described for “xyloid lignite or fossil wood” with perhaps the
exception that Jet is slightly older.
Yes, jet is not just ordinary coal. But there really isn’t any such
thing as ordinary coal. The term covers a very broad range of
materials. Some coal, such as hard anthracite is almost metamorphic,
being almost to the stage of conversion that it gets close to
graphite, while others, such as the youngest of the lignites, are not
converted too much past the stage of a partially carbonized peat bog,
with as little as 25 percent carbon content and still a lot of
Jet is distinct in it’s age, the type of water the wood originally
was deposited in (salt/fresh), the type of wood itself and the
"driftwood" nature of that wood. So the material is distinct as a
type. But it IS a type of coal. It’s distinct characteristics make it
very suited to the gem material uses it’s put to. But put it in your
furnace or stove, and it will burn just like other lignite coals will
do. A distinct material different from other coals, yes of course.
But it’s still a type of coal.
By the way, the Whiteby web page you like to starts it’s first
paragraph with an incorrect statement. It calls jet a semiprecious
stone. Jet is a fossil, but an organic one. It is, as the page says,
a unique type of fossilized wood. That is not stone nor mineral. But
The page also says “fossilized wood”. That is correct. But it would
be better if more completely described as being partially carbonized
as well. Once you do that, you’ve almost also described the similar
subtype of lignite coal called zyloid lignite. The main difference is
that most zyloid lignite is from the early tertiary period, while
Jet, at least that from Whitby, is rather older.
You can split hairs on whether to call the stuff one thing or
another. It certainly deserves it’s own gem name, “Jet”. But it’s
also accurate to include it as a type of coal, a term which
encompasses a broad range of related carbonized organic matter