Common products of burning coal are "clinker," which is, generally, the
slate or other stone and impurities found in even fine coal, and which
remains uncombusted when coal is burned.  Also "slag," probably not
correctly called by this name, which looks like waste from smelting or
forging iron--this seems to be produced as another impurity in, and
by-product of, burning coal.  "Clinker" is so named for the sound it
makes when raked out of a boiler firebox.  Together, clinker and this
"slag" are called cinders, and have been used as rough pavement or
roadbed, as railroad roadbed and ballast (not at all of the same quality
as stone ballast), and as the aggregate for cinderblock, before this
name was transferred to mean blocks cast from concrete.  In my
experience on industrial sites, coal leaves very little that it
recognizable as ash, though the clinker, slag, and pieces of unburned
coal are very, very abundant in areas where coal "ash" was disposed of.
I am speaking, here, of several sites I have recently worked on in New
York State, where the coal (from historical evidence, and the appearance
of the unburned pieces) appears to be anthracite, readily available from
northeastern Pennsylvania.  Perhaps bituminous or soft coal could
produce the fine ash you are describing?

Or, is this "black sand" actually small particles of unburned coal?  In
that case, it is, probably, "coal dust," and represents small particles
of coal left behind from coal piles used to fuel locomotives, or perhaps
stationary boilers at trackside--any association of these features with
water tanks?  In the 19th century, tanks fed from ground water had
either windmills (most common) or steam-powered pumps.  If a coal pile
was completely removed, the coal dust might remain, and mark its former
position.

D. Babson.


-----Original Message-----
From: HISTORICAL ARCHAEOLOGY [mailto:[log in to unmask]] On Behalf Of
Robert Leavitt
Sent: Monday, October 18, 2004 10:35 PM
To: [log in to unmask]
Subject: Coal (?) Ash Deposit

Hi all.

        I've been monitoring the excavation of a trench for the railroad
through
Reno, along the original transcontinental route. One of the things we've
found is a substance that is similar to coarse sand in grain size,
texture,
and ability to pack (I couldn't get vertical walls, they all ended up
being
at the angle of repose...) and a uniform black that rubs off on your
hands,
clothes, etc. Normally, there's nothing else in the deposit. A couple of
deposits have been rather random in shape, but one was in an
approximately
cubical hole about 1 meter on a side. I was thinking that it could be
the
remains of coal used in the train boilers, consequently subjected to
high
and extended heat. But coal isn't a common fuel in the Great Basin, so I
have no idea what coal ash should look like. Could someone accustomed to
coal-fired heat give me a clue what remains when coal is well burned?
Ashy
(like wood)? Mottled color or uniform? Black or shades of grey? Can I
expect a scent after its been buried for a century (I detected none)? Or
??? Unfortunately, I have no picture, but visualize black sand.

Robert C. Leavitt