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BOOK V
95
it
occurs in thick beds. In Livonia they make lamps of the very thin beds
since they are not affected by fire. Today chemists mix the silver
colored mineral with copper and other materials and make it so white
that it resembles silver. Potters sprinkle this mineral on their jars
to give them a silvery luster. They make table tops out of the
silver-lead colored mineral that occurs in thick beds. These can be
cleansed by both water and fire when soiled.
Mica is similar in color to magnetis but
has dissimilar qualities. It is the color of silver but is destroyed by
fire. It occurs in stones, marbles and sands and having originated in
these it cannot be separated. Our miners sometimes call it by a name
signifying its luster11 and at times by a name derived from the names feles and argentum)12 Some call it magnetis.13
Just as mica is the color of silver, ammochrysos (phlogopite)
is the color of gold. The sand is more the color of gold than the solid
mineral, hence the name and not as Pliny writes because it resembles
sand mixed with gold. Our miners call this mineral by a name derived
from the words feles and aurumu although it contains no gold. The golden powder that writers use instead of sand is made from it.
A similar mineral is that which the miners call armatura (slickenside)
because it polishes iron and resembles copper. However, it contains
neither of these metals, in fact not even a trace of any metal can be
produced from it. From its appearance it might have been the result of
an unsuccessful attempt on the part of nature to make a metal. A stone
that is clothed with this "armour" might be called hoplites, from
the Greek. A cleavable stone is often so "armoured" and sometimes one
side of a vein, for six feet or more, may shine like polished iron.15 Similarly ammonis cornu and
other things are "armoured" but the "armour" of these is seen to be
made, as a rule, from polished gold or brass, as I shall mention later.16
11 Glimmer.
12 Katzensilber.
13 It would appear that magnetis and mica were
distinguished primarily by mode of occurrence, the latter occurring in
veins and hence consumed when the ores were smelted. It should be noted
that Agricola distinguished talc and mica. The following description of
mica is given in Bermannus, p. 454,
Ancon. ". . . and a third mineral is white and sparkles in this rock like stars.
Bermannus. "It is as you say and I believe that this is the mineral the Latins called mica and the German miners mica and
'cat's silver' or in their language 'katzensilber.' It is called
silver because it is so similar in color to that metal that it often
deceives boys and people who do not know about mines. The term 'cat' is
used either because of the similarity of this mineral to the shine of a
cat's eye at night or because they wish to compare it to the
uselessness and worthlessness of a cat's voice. Nothing valuable is
ever obtained from this mineral when it is smelted since it is entirely
consumed in the fire."
14 Katzengold.
15
Agricola is describing a slickenside or wall of a fault that has been
polished by movement. Slickensides often have a high luster and are
common in shales that have been folded.
16 Ammonis cornu is an ammonite which here has been replaced by pyrite or marcasite.
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