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134 Kindle — Unconformity at the Base of the

least of the fishes credited to the Huron shale by Newberry
and unknown in the Cleveland, came, not from the Huron,
but from the Olentangy shale at tlie base of the Huron. This
conclusion is evident from the remarks concerning CaUogna-
thus regularis on page 60 of Newberry's monograph* although
it is referred under the description of the species to the Huron
shale. With increasing knowledge of the fish fauna of the
Huron we may confidently expect the discovery of a consider-
able number of species common to both the Huron and the
Cleveland shales. The general resemblance of the conodont
faunas of the two formations seems fully to justify this pre-
sumption. The writer's collection from the fl!uron shale will,
when studied, it is believed, add other species of fishes to those
which are known to be common to the Huron and Cleveland
shales.

Professor Newberry, in his latest reference to the conodonts
of the Cleveland shale, dismissed the evidence which these fos-
sils might have yielded him with the statement that "the mil-
lions 01 conodonts in it have no geological significance."t This
view is evidently not shared by Dr. Bassler, who has based his
correlation of the Chattanooga^ shale of Tennessee and the
Cleveland shale of Ohio entirely on the similarity of the
conodont faunas in the two. Nor is it shared by the writer,
although, as previously stated, detailed discussion of the evi-
dence which this group will afford must wait the description
of the conodont faunas recently discovered by the writer in
the Huron shale in northern Ohio. A preliminary examina-
tion of the conodont fauna of the Huron shale shows that it is
very similar to that of the Cleveland shale. The most impor-
tant facts now available, as bearing directly on the question of
the age of the Cleveland shale, relate to the known range
outside of Ohio of the species which have been recognized in
it. Only three of the Cleveland shale species of conodonts
have thus far been recorded from other formations. These
are Prionides angulatus Hinde, Prionidea erraticics Hinde,
and Polignathua dubius Hinde. These species are recorded
only from Hamilton and Genesee horizons:]: elsewhere, so that

• Mon. U. S. Geol. Survey, No. 16. 1889.

f Mon. U. S. Geol. Survey, xvi, page 128, 1889.

X Hinde, Geor{<e H., On Conodonts from the Cbazy and Cincinnati Group
of the Cambro-Silurian, and from the Hamilton and Genesee-shale Divisions
of the Devcgaian, in Canada and the United States. Quart. Jour. Geol. Soc,
London, vol. xxxv, pp. 351-368, 1879.

Clarke, J. M., Annelid Teeth from the lower portion of the Hamilton
Group and from the Naples Shales of Ontario Co., N. Y. N. Y. State Geol.,
Sixth Ann. Rep. for 1886, pp. 30-33, pi. Al.

Grabau, A. W., The Paleeontology of Eighteen Mile Creek and the Lake
Shore Sections of Erie Count v, New York. Bull. Buffalo Soc. Nat. Sci.,
vol. vi, pp. 150-158, figs. 38A-^8I, 34-46, 1899.



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Chattanooga Shale in Kentucky. 135

the conodonts, so far as their evidence is recorded, indicate a
Devonian age for the Cleveland shale.

Resume of conclusions concemiiig age of unconformity. —
Briefly summarizing the discussion of the question of the age
of the Cleveland shale, we may say that (1) the evidence of
the Waverly fauna originally brought forward by Newberry
and restated by Bassler should be eliminated from considera-
tion, because neither Newberry nor any of bis successors have
been able to substantiate it by finding a similar fauna at the
base of the Cleveland. (2) Later workers have failed to find
any of the Carboniferous fishes claimed by Newberry to occur
in it. (3) Some of the large fossil fishes which characterize
the Cleveland are represented by identical species in rocks of
demonstrated Devonian age. (4) The Cleveland shale cono-
donts, so far as their range has been recorded, are known
elsewhere only from Devonian rocks.

If there is extant no valid evidence of the Carboniferous age
of the Cleveland shale, as the preceding review of it appears
to indicate, the correlation of the Chattanooga shale, either in
part or in toto with the Cleveland, affords strong evidence for,
instead of against, its Devonian age as has been assumed by
Dr. Bassler. This evidence in the north is fully corrobo-
rated in the south by the discovery of a conodont fauna in a
black shale of admitted Devonian age in east Tennessee which
is identical with that in the Chattanooga shale. Thus we see
that correlation of the Cleveland shale with its equivalent or
partial equivalent, both in northern Ohio and eastern Tennes-
see, indicates its Devonian age.

With respect to the unconformity at the base of the Chatta-
nooga shale, the important and obvious fact which appears
from this discussion of the age of the Chattanooga is, that it
does not transgress Devonian time. The field work of the
writer has furnished convincing evidence, both stratigraphic
and faunal, that the Chattanooga shale in Kentucky represents
the Huron as well as the higher beds of the Ohio shale. Detailed
presentation of the faunal and stratigraphic evidence of the
continuity of the Huron shale across Kentucky must, however,
await the appearance of the writer's report on the fauna and
stratigraphy of the Chattanooga shale. Only the evidence
of one of the fossil fishes will be introduced here. Dr. L.
Hussakof writes* concerning one of the fossil fishes obtained
from this horizon by the writer and Mr. P. A. Bungart on
Copperas Creek, east of Indian Fields, Clarke Co., Kentucky,
as follows :

" The specimen from Copperas Creek is without any question
Dinichthys herzeri Newberry, the species supposed to be indica-

* A letter to the writer, Nov. 28, 1911.



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136 Kindle — Chattanooga Shale in Kentucky.

live of the Huron shale. Your specimen shown even the series
of denticles along the front face of the * premaxillary ' just as in
the type specimen."

The fauna which most geologists have held to indicate a
Genesee age for the Chattanooga in Kentucky the writer has
found on all sides of the Cincinnati arch in Kentucky, but
confined to the lower beds of the formation. There appear to
be no good grounds for questioning this assignment of the
basal beds of the Chattanooga to Genesee time. The land
conditions represented by the unconformity could not then
have continued later than the Genesee. Their initiation could
not have been earlier than late Hamilton. Limestone of this
age underlies the shale near Louisville. Hamilton fossils
have been found in the Harpeth River valley a short distance
south of the Kentucky-Tennessee boundary. When tl)e Devo-
nian limestone has been carefully studied in the intermediate
territory in Kentucky, Hamilton fossils will doubtless be
found in various localities where the rocks of this age have
partially escaped erosion. It would appear, therefore, that
the unconformity involved a time representing either early
Genesee or late Hamilton time, or both.

The evidence available with regard to the age of the black
shale sediments in eastern Tennessee and southwest Virginia,
indicate land conditions that were contemporaneous with
those which have been described in Kentucky. The uncon-
formity at the base of the Chattanooga shale in eastern
Tennessee* indicates that a land area existed in that region
previous to Chattanooga sedimentation which was doubtless
continuous with land conditions in southwest Virginia and
central Tennessee and Kentucky, but which may have begun
at an earlier period than in Kentucky. The unconformity in
eastern Tennessee and southwestern Virginia is followed by
shales with a fauna similar to that which we find above it
in the Chattanooga in Kentucky. We must conclude, there-
fore, that while pre-Chattanooga land conditions may have
begun considerably earlier, they did not last appreciably longer
in eastern Tennessee and southwest Virginia than in Kentucky.

* Keith, Arthur, KnoxvUle, Loudon, MayuardsvUle, and Morristown
FolioB, U. S. Geol. Survey.



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Washington — Suggestion for Mineral Nomenclature. 137



Abt. XVllI. — A Suggestion for Mineral Nomenclature / by
Henry S. Washington.

Introduction. — That the science of mineralogy may be
regarded as a branch of descriptive chemistry (but one which
deals only with substances occurring in nature) is recognized
in the prevalent mineral classifications, where the chemical
composition is the primary and most important factor. The
character of the negative (acidic) ion controls for the for-
mation of the largest classes, and subclasses may be based on
the character of the positive (basic) ion, in some cases preceded
by separation into anhydrous and liydrated compounds. In all
these subclasses minerals which belong to the same acidic type
are placed together. The ultimate smallest groups, which
bring together minerals regarded as most closely related, are
based on similarity in crystal form, dependent on isomorphous
replacement, either entire or partial, and either in the negative
or the positive portion of the molecule; while again dissimi-
larity in crystal form due to polymorphism of substances with
the same empirical chemical composition, serves to distinguish
between groups chemically alike.

The crystal form, therefore, is a necessary diagnostic, as
important for the formulation of our idea of any mineral as
its chemical composition. As Miers* expresses it, for the defini-
tion of minerals "we are forced to employ at least two proper-
ties, namely the chemical composition and the crystalline
form: these two, when completely known, are necessary and
sufiicient for the definition and determination of any mineral."
The less important characters, such as color, structure, habit,
state of aggregation, and minor details of chemical composition,
are (or should be) used only to distinguish very subordinate
(varietal) divisions, and, as Miers justly says, far too much
importance has been generally assigned to them in naming
minerals. Many cases will also occur to every mineralogist
of minerals which stand alone and can only be referred to
indefinite positions in the classes, dependent on the general
character of the negative ion ; that is, they show no intimate
relations with other minerals through both their chemical and
crystallographic characters and constitute the sole represen-
tatives of potential groups, which thus correspond to the mono-
typic firenera of botany and zoology.

In this necessary utilization of both chemical composition
and crystallographic characters, the definition and classification
of minerals diflEer from, and may justly be considered as in

*H. A. Miers, Mineralogy, London, 1902, p. 2.

Am. Joxtr. Scj.— Fourth Skriks, Vol. XXXIII, No. 194.— February, 1912.
10



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188 Washington — Suggestion for Mineral Nomenclature.

advance of, the classification and definitions of descriptive
chemistrv, which only take cognizance of the ultimate chemi-
cal composition of the substance as revealed by analysis, and
its molecular structure as shown by its reactions, replacements,
molecular weight, etc. To the chemist, CaCO, is only calcium
carbonate, whether its crystal form is trigonal or orthorhombic,
with correlated differences in specific gravity, optic characters,
etc. To the mineralogist these two forms are different min-
erals, though the chemical composition is expressed by the
same empirical formula.

This recognition of polymorphous or physically isomeric
forms of the same empirical molecule as different substances
and the converse relationship between substances of closely
similar crystal form and of the same chemical type, though dif-
fering in composition through isomorphous replacement, is
but a logical following out of the teachings of physical chem-
istry. It is an extension of the definition of "substance" to
include, in addition to the chemical composition, the relations
of the physical and chemical characters of matter to the con-
ditions of equilibrium which control crystallization. That the
recognition of the essential difference between substances (in
this sense) with the same ultimate chemical composition is
valid and necessary, is shown by consideration of such cases as
diamond and graphite (C), pyrite and marcasite (FeS,), or caI-
cite and aragonite (CaCO,). In these the differences in the
physical characters, and to no less an extent in many of the
chemical characters, as resistance to reagents, of the members
of each pair are so great that they must be regarded as dis-
tinct substances. This would be true even from the purely
chemical point of view, since the physical differences, espe-
ically those like specific gravity and specific heat, indicate
differences in the molecular weight and very probably in
molecular structure.

It may be noted here that among minerals there are few
ascertained cases of chemical isomerism, in which the distinct
physical and chemical characters, due to profound and persist-
ent differences in the molecular structure, persist after the sub-
stance has been changed into an amorphous state, as by fusion
or solution, and then recrystallized.* Numerous illustrations
of this ai'e furnished by organic chemistry, the most classical
being that of urea and ammonium isocyanate. Among
minerals it is diflBicult to prove the existence of such cases,
though they unquestionably occur, and Grothf regards pyrite
and marcasite, and cyanite, sillimanite and andalusite, respec-

* Groth, Introduction to Chemical CrystaUography, New York, 1906, p. 3.
t Qroth, Chemische Krystallographie, Leipzig, Pt. I, 1906, p. 155, and
Pt. II, 1908, p. 258.



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Washington — Suggestion for Mineral Nomenclature. 139

tively, as cases in point. Whether there is any essential dif-
ference between physical and chemical isomerism may perhaps
be doubted, but further discussion of this topic is uncalled for
here.

In spite of this advanced state of the classification of min-
eralogy, the nomenclature is in much the same condition as in
the time of Pliny, when minerals were named after their qual-
ities, localities, or uses, with the systematic termination -ites
or 'itis (modern 'ite\ the only innovations being the intro-
duction of names after persons and certain other arbitrary ter-
minations. Despite attempts to introduce binomial names,
analogous to those of botany and zoology, or those based on
chemical characters, systematic mineralogy has adhered closely
to the nomenclature of the first century A. D*

As a consequence, mineral nomenclature, like that of the older
rock classifications, is unable to express the facts of classification.
Roots derived from names of places or persons can convey in
themselves absolutely no idea of the mineralogical characters,
and even those derived from chemical -or physical characters
are applicable to many different minerals. Thus cuprite
applies equally well to CuO as Cu,0, and octahedrite would be
an appropriate name for magnetite, franklinite, or fluorite.
All such name roots are purely arbitrary in their mnemonic
connotations, but at the same time, by long association, a laige
proportion of mineral name roots convey very definite ideas of
the mineral and chemical characters.

Again, with the uniform and monotonous general use of a
single termination (-ite), and the arbitrary and unsystematic
employment of others, the characters and relations of minerals,
and even of mineral groups, are concealed. No distinction is
evident from the name between a rare or uncharacteristic vari-
etal form of a certain mineral (as hiddenite or sagenite), and
a large mineral group which may include manv distinct min-
erals (as zeolite or chlorite). In the case of a few of the com-
monest and largest groups of related minerals we have names,
fortunately distinctive because of their terminations, which
may be applied to the group as a whole, as spinel, feldspar,
garnet, pyroxene, amphibole, mica ; and the general usefulness
and common application of these is sufficient evidence of the
value of such group names. In other cases the difficulty of
expressing relationsnips is got round and the need supplied by
the word "group" after the name of a typical representative :
as the pyrite, calcite, aragonite, olivine, and apatite groups.
In all these group names the underlying idea wnich connects
the members is adherence to a certain type of chemical formula,
with isomorphous replacement, and, of equal importance, close
• Cf . Dana, System Mineralogy, 1893, p. xl.



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140 Washington — Suggestion for Mineral Nomenclature,

similarity in the crystal form as shown by the system, axial
relations, and often cleavage. As regards the crystal system,
in the largest groups this similarity need not amount to iden-
tity, as in the feldspars, pyroxenes and amphiboles, but in gen-
eral the idea of a mineral group implies identity of crystal
system modified only in its details by the slight morphotropic
changes consequent on isomorphous replacement.

It will thus be seen that a mineral nomenclature should be
able to express in the name a fairly definite idea of the chemi-
cal composition and type of compound, as well as the crystal
system, and at the same time indicate the relations to other
minerals, and especially the membership of a mineral in its
particular "group." It is the object of this paper to lay stress
on the importance of the recognition in mineralogical classifi-
cation of this idea of mineral groups, distinguished by close
similarity in chemical composition and crystal form, and made
up of distinct mineral members, and to suggest a nomenclature
wnich will express these relations, based on the general princi-
ples of chemical nomenclature, but providing also for the
recognition of the crystal form as an element of the classifica-
tion.

The System of Nomenclature. — As compared with the car-
bon compounds, minerals, and especially the silicates, present
very great diflSculties in the study of their molecular constitu-
tion. This is because of their high fusing points, non-volatility,
insolubility, general chemical stability at ordinary or even very
high temperatures (so that replacements of portions of the
molecule are diflicult), and impossibility of determination of the.
molecular weij^ht, assuming that the term " molecular weight "
is applicable to a solid body. Although we now realize the
importance of this branch of mineralogy, and are beginning to
recognize, especially among the silicates, the complex chemical
constitution of many minerals and the existence of certain
radicals or atomic groups analogous to those of organic chem-
istry, yet we are generally forced to be content with the expres-
sion of the chemical composition by simple empirical formulas.
The constitutional and graphic formulas of but very few min-
erals can be given witli any degree of confidence, and in the
vast majority of cases we are absolutely in the dark.

Mineralogy is essentially in the condition of organic chemis-
try of the early days, when the composition of alcohol could only
be expressed empiricalh^ as 0,11^0, that of lactic acid as C,H.O„
and that of urea as CH^ONg; whereas at present we can confi-
dently express them by the constitutional formulas, (C,H,)
(OH), (CH.) (CIIOH) (COOH), and (CO) (NH,)„ systemati-
cally known as ethyl alcohol, a-hydroxypropionic acid, and
carbonvl amide, the last differing in constitutional formula
from the isomeric ammonium isocyanate, (CON) (NHJ.



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Washington — Suggestion for Mineral Nomenclature, 141

Indeed, the theory of mineral constitation at present is in
many ways analogous to the "theory of types" in organic
chemistry, formulated by Gerhardt about 1850, as is seen in
the general reference of the silicate minerals to simple silicic
acids, H,SiO„ H,SiO„ H,Si.O„ etc. Kekul6's " theory of linked
atoms" has now superseded this in organic chemistry,* and
the applicability of this to mineral chemistry has only recently
begun to be realized.

The study of the molecular constitution of minerals and
attempts at the establishment of constitutional formulas have
been undertaken by Tschermak, Groth, Clarke, and many others,
either through direct experiment or study of alteration pro-
ducts, but so far with doubtful success in most cases, and it
will probably be many years before mineralogy attains to the
knowledge requisite for formulas like those of modem organic
chemistry.

In three important papers Penfieldf established the complex
character of the acidic portion of the tourmalines and amphi-
boles, and showed the effect of the mass action of the complex
acid in controlling crystallization, allowing replacement of the
hydrogen atoms of the hypothetical acid by very different ele-
ments or radicals, and with different valences, but without
change in crystal form. He also speaks of these acids as tour-
maline acid and amphibole acid, with the implication that an
essential character of their salts is adherence to the particular
crystal form of tourmaline and amphibole respectively.

More recently the problem of tlie constitution of some sili-
cates has been studied by Tschermak, Baschieri and othets4
These investigators have identified certain silicic acids, which
they call after the mineral names, among them being: anorthi-
tic acid (H,Si*0,) albitic acid (H,Si,0,), leucitic acid (H,Si,0,),
heulanditic acid (H^Si^O,,), granatic acid (H^Si.O, and dato-
litic acid (H,Si,Oj). Their method, it may be remarked, does
not apparently permit of discrimination between a purely sili-
cic or an alumo- or boro-silicic acid, and none of these workers
suggests, like Penfield, that the acid or the acid name implies
the crystal form of its salts.

It is suggested here that this concept of Penfield of silicate
minerals as salts- of mineral acids, in many cases of much
greater complexity than is implied by the empirical formula,
with the implication of the adherence of the salts to a charac-

* Cf . C. Schorlemmer, Rise and Development of Organic Chemistry, Lon-
don, 1894, pp. 89. 69, and 155.

tThis Jonmal, vii, p. 97, 1899: x, p. 19, 1900; xxiii, p. 23, 1907.

tTscl^prmak, Sb. Ak. Wiss. Wien, cxii(l), p. 355, 1905, cxiv(l),p. 455,
1905, cxv(l), p. 217, 1906. E. Baschieri. Proo. verb. Soc. Tosc, xvi, p. 34,
1907; Atti Soc. Tosc. Mem., xxiv, p. 133, 1908. Himmelbauer, Sb. Ak.
Wiss. Wien, cxv(l), p. 1184, 1906.



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142 Washington — Suggestion for Mineral Nomenclature.

teristic crystal form, be extended to minerals in general and
made the basis of a mineral nomenclature. From this point of
view silicate minerals would not be considered simply as salts of
orthosilicic acid (H.SiOJ, metasilicic acid (H,8iO,), disilicic acid
(H,Si,Oj), and so forth ; as substitution derivatives of normal
aluminum silicates according to Clarke, (which correspond to
the old theory of types) ; or of multiples of silica according to
Goldschmidt : but each group would be considered as salts of a
particular silico- or alumino-silico- acid characterized by the parti-
cular crystal form and symmetry of its salts, and capable of
ismorphous replacement either of its basic hydrogens or in the
acidic portion.

This concept may be most appropriately applied to mineral
groups, distinguished as at present by identity of chemical
type and close similarity in crystal form, but it may be equally
well applied to monotypic "groups", represented, so far as no\^
known, by only one mineral and which exhibit no evident
near relationships, either chemical or crystallographic, as is the
case with beryl and calamine. It is also clear that it would
be applicable to minerals of simple as well as highly complex
constitution. A further point, and one of gi'eat importance,
is that a system of nomenclature based on this concept would
be applicable whether the structural or constitutional formula,
or even the exact chemical composition, of the mineral acid
were known or not, as the salts oi a given mineral acid (in this
sense) would be identifiable and their relationship established
by their conforming to a certain empirical chemical formula
and crystal form. Thus the various pyroxenes and amphiboles
are members of two different, but well-characterized, and uni-
versally recognized "natural" groups, though we are as yet
almost wholly ignorant of their molecular constitution, know-
ing only that they may be referred, but do not necessarily be-



Online LibraryJohn Elihu HallThe American journal of science → online text (page 14 of 61)