7
INTRODUCTION
In the chapter on characteristics of the industrial minerals sector, a broad definition of industrial minerals and rocks is discussed—a definition that must embrace solids, liquids, gases, minerals, rocks, gems, glasses, wastes, and some manufactured products—each cat-egory with its own range of uses. Clearly, industrial minerals and rocks do their utmost to defy simple definition and are linked as closely by their differences as by their similarities.
To bring some order to this disparate field, a classification sys-tem is needed to highlight the commonalities and contrasts in a structured way. Any robust classification must address the needs of a wide range of potential users that may include (but is not limited to) academics, industrial geologists, industrial raw material users, specifiers, product formulators, technologists, engineers, managers, and financiers and investors. Given their different priorities, focus of attention, and backgrounds, it is not surprising that no single approach is universally adopted.
CLASSIFICATION SCHEMES
A range of classifications based on a variety of commodity criteria has been used over the past 50 years or more as tools for under-standing the geological context, market uses, defining properties, economic contribution, and statistical significance of industrial minerals and rocks. Each approach has its strengths and weak-nesses, and any durable scheme in such a dynamic industrial sector will inevitably present only part of the picture. Bates (1975) exam-ined a number of these schemes, and more extensive comparisons have been undertaken by Kuzvart (1984), Noetstaller (1988), and Smith (1999). All of these were drawn on extensively for this review.
Berzelian
The world of systematic mineralogy has a number of classification systems that have also been applied to industrial minerals. Most museum mineral collections are catalogued by the Berzelian classi-fication system, which is based on elements, ions, ionic groups, and compounds such as halides, oxides, carbonates, and silicates, among others. This system was used in early accounts of the non-metallics (such as in Merrill 1904) and also hydrocarbons, but not industrial rocks other than some siliceous and calcareous examples under silica and calcium carbonate, respectively. The classification did not cover waste materials, brines, or most manufactured
prod-ucts because many of these were yet to be recognized as important raw materials or products.
Alphabetic
The simplest approach, and certainly the most intuitive and accessi-ble for those from outside the subject seeking commodity-specific information, is nothing more complex than the alphabetical listing of commodities. This has been adopted for systematic commodity reviews in earlier editions of this book (e.g., Lefond 1975; Carr 1994). Indeed, as noted by Harben and Bates (1984), the “alphabetic treatment neatly sidesteps the vexatious matter of classification.”
This edition in part adopts the same approach as it lends itself to simple encyclopedic interrogation once a mineral or commodity is identified. Approximately 60 commodities are typically included in such a listing, but these are always under review. This simplistic compositional approach works reasonably well for industrial min-erals but requires a degree of clarification and consistency because subdivisions are often necessary. For example, clays can be divided into bentonites, which can in turn be divided into sodium or cal-cium smectites. Nomenclature for industrial rocks and other raw materials can also be variable; for example, brick clay, common clay, structural clay, and heavy clay are all common pseudonyms and are based more on application than composition.
Unfortunately, the alphabetic approach to classification obscures many important links between commodities, including similar properties they possess, geological processes that led to their formation, or applications in which they are used. For this reason, the alphabetic classification employed in this edition is supple-mented by important reviews of major markets and uses for indus-trial minerals and rocks. Although this approach may suit those using a book format, other forms of classification have been devel-oped that may be more useful for the consumer or the geologist. Geological Processes
From the geologist’s perspective, there is much to be gained by try-ing to place a genetic classification on such a wide variety of materi-als (Bates 1960; Harben and Bates 1984). There are well-defined categories of geological processes responsible for the formation of all minerals and rocks, and industrial minerals and rocks encompass the complete spectrum. Such a classification parallels standard geo-logical understanding and has exploration relevance because a com-modity may be found again in other places where these processes
Industrial Minerals and Rocks
dominate. Because particular geological processes often result in a range of similar products, there is also some natural grouping of physical properties, although this is far from uniform.
The dominant divisions have been igneous, sedimentary, metamorphic, and surficially altered minerals and rocks (Harben and Bates 1984). Igneous subdivisions were intrusive, extrusive, pegmatitic, and hydrothermal; sedimentary was divided into clastic, biogenic, and chemical. Because this is principally a geological cat-egorization, waste and processed materials were not specifically addressed. In their follow-up account of world deposits (and after much deliberation; P. Harben, personal communication), the same authors reverted to an alphabetic arrangement of commodities, allowing very different deposit types to be discussed under individ-ual commodity headings (Harben and Bates 1990).
Lorenz (1991) produced a more detailed tabulation of geolog-ical origins for industrial minerals deposits, along with a similar analysis of deposit sizes and many other economic, technical, and end-use parameters.
Tectonic Models
Although mainly developed as exploration models, these block dia-grams have, in effect, produced a tectonic classification of deposit types for particular commodities (Figure 1; Anon. 1994; Highley
1994). They are therefore a development of the geological process classifications and have the major advantage of allowing analysis of the potential spatial, as well as geological, relationship between dif-ferent industrial minerals. This makes the approach an ideal one for industrial minerals exploration and parallels the earlier work under-taken for metal deposits (e.g., Mitchell and Garson 1981; Sawkins 1984).
Important Properties
As the phrase “industrial minerals and rocks” implies, each com-modity has some commercially significant composition or property on which its use is based. Kline (1970) devised a simple twofold division: chemical minerals, where their main purpose is as the source of important elements (e.g. industrial minerals and rocks used in the fertilizer, chemical, ceramics, and metallurgical indus-tries); and physical minerals, where the minerals do not signifi-cantly change in composition during use. Important features of this latter group, which include many construction materials, abrasives, foundry supplies, gems, and fillers, would be their physical proper-ties such as particle-size distribution, brightness, and surface area.
These considerations have become central to many later clas-sifications but usually as one part of a more complex set of classifi-cation criteria.
Source: Anon. 1994.
Figure 1. Industrial mineral deposits found in active continental margins
Air Fall Ash (Fine) Pumicite, Pozzolana
Air Fall Lapilli (Coarse)
Pumice Lateral Cinder Cone
Scoria Runoff High in Dissolved Silicon
Caldera Subsidence Lake Sediments Bentonite, Zeolite, Diatomite
Rhyolite Dome
Perlite AggregateLava Flow Dimension Stone
Ash Flow Tuff Pumice, Dimension Stone,
Aggregate
Fore Arc
Basin Fore Arc Fummaroles Sulfur Beach Sands Olivine Oceanic Trench
Hydrothermal Alteration of Volcanics Bentonite, Kaolin
Ophiolite: Ultrabasic Rocks Chromite, Dunite, Serpentinite, Magnesite
Ophiolite:
Pillow Lavas and Sediments Ochre, Umber
Alluvial Fans Aggregate
End-Use Classifications
It is a common saying in the industrial minerals and rocks sector that “exploration begins with markets” (Coope 1982). This highlights the essential importance of understanding that the mineral or rock has value only if there is a customer willing and able to pay for it. Min-erals are, however, capable of being utilized in many different end uses; limestone, for example, can provide more than 100 separate products that are used in very different applications. Equally, some consuming industries require a suite of different industrial minerals, each of which alone would not meet the needs of the manufacturing process. For these reasons, many classifications have concentrated on either the end uses for minerals and relationships between them, or combined end uses with other important parameters of the indus-trial minerals and rocks industry.
Following the work of Bates (1959) and Wright and Burnett (1962), Fisher (1969) conducted a detailed analysis and defined six major end-use groupings that were characterized by variation in unit value, production volume, and associated parameters:
1. Bulk construction and building materials
2. Bulk ceramic raw material (in addition to lime and diversified industry raw materials or products)
3. Specialty building products and principal refractories 4. Major industrial chemicals and fertilizer raw materials 5. Industrial minerals and rocks
6. Specialty-grade and precious minerals and rocks
For each group, Fisher also presented a series of graphs showing the typical levels of capital and plant cost, place value, resource spread, enrichment ratios, and fiscal treatment, based on deposits and compa-nies in the United States. Although the groupings are defined on end uses, this represents one of the earliest and most rigorous attempts at a multifaceted classification for industrial minerals and rocks.
In a major review of nonmetallic mineral deposit assessment criteria, Lorenz (1991) produced a detailed tabulation of commodity uses in some 38 products or intermediate products. Highley (1994) adopted a more straightforward graphical attempt to illustrate impor-tant sectors with a hierarchical chart of major end users. Chang (2002) also produced an account of the industrial processes and end uses for the main industrial minerals and rocks and noted that they could be allocated into 16 groupings based on their function or final product.
Although not an attempt at a rigorous classification, the end uses for ground (filler and extender) minerals are examined from a “formulator’s” viewpoint in Ciullo (1996). Although this represents only a section of both consuming industries and industrial minerals and rocks, it provides a useful way of examining the diverse roles that different minerals play in products and their ability to substi-tute for each other.
Economic
As part of their objective to inform Californians about their state’s geology, mineral deposits, and general usefulness of minerals and rocks, Wright and Burnett (1962) proposed a threefold “commer-cial” classification of industrial minerals and rocks. Based on unit price and production volumes, the groups were
1. Low price–large volume: materials used in construction such as aggregates, gypsum, and common clay
2. High price–high volume: borates, potash, and salt
3. High price–low volume: barite, kyanite, beryl, mica, and talc Each group was also identified as having a number of common fea-tures in terms of their deposit size, distribution, location, mining methods, and treatment.
Bates (1969) developed his own twofold subdivision based on an analysis of similar high and low unit-value commodities. This also involved examining the bulk, place value, imports and exports, and distribution and geological or processing complexity that typi-fied each group. He concluded that because most industrial
miner-als fell into the high unit-value group, while industrial rocks mainly
fell in the low unit-value group, these should form the basis of a simple classification. In this scheme, rock salt is regarded as a rock, while potash a mineral—a slightly arbitrary attribution that fits bet-ter with the typical characbet-teristics of other commodities within each group (Table 1).
From a systematic economic perspective, Noetstaller (1988) produced a highly illuminating analysis of the industrial minerals and rocks sector in his report for the World Bank. Although again not principally for classification purposes, the lists and graphs pro-duced for ranking and economic comparisons offer much insight into the ranges and clustering of industrial minerals and rocks com-modities under many economic, trade, technical, and even geologi-cal parameters. Examples include commodity lists by unit value, concentration of production in certain countries, the proportion of each commodity’s production that is traded internationally, and a
Table 1. Industrial minerals and rocks classification based on end use and genetic subdivision
Aspect Group 1 Group 2
Bulk Large Small
Unit value Low High
Place value High Low
Imports and exports Few Many Distribution Widespread Restricted
Geology Simple Complex
Processing Simple Complex
Industrial Rocks Industrial Minerals Igneous Rocks Igneous Minerals
Basalt and diabase Beryl Granite Feldspar Perlite Lithium minerals Pumice and
pumicite
Mica
Nepheline syenite
Metamorphic Rocks Vein and Replacement Minerals
Marble Barite Slate Fluorspar
Magnesite
Sedimentary Rocks Quartz crystal Clay Metamorphic Minerals
Gypsum Asbestos Limestone and
dolomite
Graphite Talc Phosphate rock Vermiculite
Salt Sedimentary Minerals and Sulfur
Sand and gravel Borates Sandstone Diamond Diatomite Nitrates Potash minerals Sodium minerals Sulfur
contrast of commodity production and consumption between the developing and developed world. An update of this World Bank report would be of great service to the industry.
Hybrid and Combined Methods
Bates (1960, 1969) produced a combined end-use and genetic clas-sification incorporating a simple initial division into industrial rocks or industrial minerals, with duplicated geological subdivi-sions denoting the origin within each (see Table 1).
To attempt to relate geological and economic factors, Dunn (1973) developed a matrix classification in the form of a chart with one axis as uses and processes, and the other as rock types and min-erals. The matrix incorporates the split by importance of either physical or chemical property (similar to Kline 1970), with 23 gen-eral end-use subdivisions, against which are indicated specific rocks or minerals used and their geological origins (similar to Bates 1969). The main strength of this chart was to visually highlight the versatility of some rock or mineral products, the geological envi-ronments that provided a range of economically interesting prod-ucts, and the end uses that exploit many alternative or complementary mineral raw materials.
Kuzvart (1984) undertook a thorough comparison of different principles on which classifications have been constructed. He favored a classification system based on a combination of genetic, end-use, and economic aspects of industrial minerals. This was achieved despite the observation that an understanding of the gene-sis, end uses, and economics of deposits develops continually, requiring frequent revision of a classification based on these fac-tors. He did, however, organize his work to encompass the twofold economic classification of Bates (1969), with an alphabetic subdi-vision of commodities supplemented by separate chapters address-ing genetic, prospectaddress-ing, and technological factors.
As a tool to assist in teaching about industrial minerals and rocks, Smith (1999) developed a classification that defined seven groups of commodities based on the relative importance of physical and chemical applications or a combination of the two. The classifi-cation is constructed using a matrix of commodities and uses that are grouped according to application. Clustering of commodities reveals the following groupings:
1. Principal abrasives—diamond, alumina, garnet, and pumice 2. Principal refractories—pyrophyllite, sillimanite group,
magne-site, and graphite
3. Principal fillers—wollastonite, titanium minerals, mica, barite, and iron oxide
4. Principal physical and chemical minerals—feldspar and zeolite 5. Mixed-application physical minerals—silica, perlite, clay, and
talc
6. Principal chemical minerals—phosphate, salt, and sulfur 7. Mixed-application physical and chemical minerals—olivine,
chromite, fluorspar, gypsum, and limestone
The matrix was also supplemented by a schematic representa-tion of the groupings in the form of a set of intersecting circles. Other Classifications
Industrial minerals are included and subdivided in all manner of other classifications, from depletion allowances to tax rates, under import duties and Bureau of Statistics classifications, and in a mul-titude of economic categories. These generally do little to illumi-nate industrial minerals and rocks as a group and will not be considered in any further detail here.
LIMITATION OF THESE APPROACHES
To exploit an industrial mineral deposit successfully, all factors need to be considered, including deposit location, quality, processing amenability, other essential raw materials, power, infrastructure, human resources, competition, marketing, packaging, transporta-tion, technical support, prices, and contractual agreements. It is therefore unreasonable to expect any classification scheme to address the full range of factors that are intrinsic to or affect each commodity or grouping. The industry is dynamic; commodities rise and fall as new applications develop or cheaper and better alterna-tives surface. Technological advances improve bottom-line perfor-mance. A classification system must adapt to these changes. A robust classification system must address the geological, composi-tional, economic, and end-use properties of each commodity.
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