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BOOK IV
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67
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his authority—because it is said to be found on the island of Samothrace. Nicander calls it lapis thracius because
farmers bring it from a Thracian river that they call Pontus. An
unknown Greek writer states that the Pontus river which carries down
this genus of stone is between Scytha and Medos. There is still a
question whether lapis thracius may be the same stone as that which Theophrastus calls spinus or the same as another stone which I shall now describe. Each of these stones is bituminous but the latter is simple, spinus complex. I shall discuss the complex minerals in the tenth book.
Obsidianus lapis is a hard bitumen which is so named because it is found in Ethiopia near Obsidius. The gem called obsidiana is
made from it. We see that one and the same thing, namely black earthy
bitumen that is often hard when it comes from the earth, is known by
all of these names. It is necessary that I be able to defend my opinion
with the words of the writers themselves. But first may I describe this
kind of bitumen.
This
bitumen is black, pitchy and resembles a poor quality of coal. It has
the luster of pitch and is sometimes soft, sometimes hard. Broken into
splinters and set on fire it burns. When the soft variety is pulverized
and placed in olive oil it dissolves rapidly, as Galen has written. I
have purchased many of these stones, tabular and black and similar to
the tablets that come from Coele, Syria, which, when placed in a fire,
burn with a meager flame. These come from the hills around the Dead Sea
and from the same locality that produces bitumen. Their odor is similar
to that of bitumen. However, without doubt the hot waters flowing deep
beneath those bituminous hills have abraded and liquefied the bitumen
and carried it into the lake or sea in which these waters have welled
up as springs. This black bitumen is later cast up by the raging and
seething of the sea and is found on the shores. It differs from the
true Judean bitumen only in hardness. The more broken material is not
tabular but differs only in this respect.
Ampelitis earth, which is also called pharmacist's earth (pharmacitis) is
the best. It is pitch black and when broken into small splinters has
the same luster as small pieces of coal. It dissolves when crushed and
mixed with olive oil, according to Dioscorides. Galen says that it
differs greatly from other earths and comes near to being the essence
of stone. From this we know it to be hard. It is known to consist of
bitumen, not so much from the writings of Pliny who says that it is
very similar to bitumen as from the writings of Posidonius who says
that it is bituminous. Since it is such a material it burns readily.
From all of these facts it is evident that ampelitis earth is
native bitumen of the finest quality and for that reason is given
preference by physicians. Bitumen that has been mixed with too much
earth is usually of another color and does not belong to this group.
It is obvious to the eyes that native coal does not differ from ampelitis earth. Theophrastus who has referred to coal makes no reference to ampelitis and, on the other hand, those who have written about ampelitis have
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