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Stone or Rock? Is there a difference? Working on Stories in Stone: Travels Through Urban Geology forced me to consider this question and its implications. Throughout the book, I use the terms interchangeably, based mostly on how they sound or how frequently I used one or the other.
When I did a bit of searching on the web, I found that some people thought that stone was more British; that rock could be hard and soft, whereas stone was always hard; that stones are smooth and rocks rough; and that stones are small and rocks are big. In his wonderful book, Stone by Stone, Robert Thorson writes “Rock is raw material in situ. Stone usually connotes either human handling or human use, although it can also be used to describe naturally produced fragments of rock larger than a cobble.”
[nggallery id=17]Seeking a more erudite source, I turned to one of my favorite books, the Oxford English Dictionary (OED), to get the fine opinion of its worthy editors. The first definition for rock is “A large rugged mass of hard mineral material or stone.” Its first use comes from Old English, dated at 950-1100. The OED defines stone as “A piece of rock or hard mineral substance of a small or moderate size,” first used in 825. Now, I see the difference!
Curiously, the word stonerock, defined as “A pointed or projecting rock, a peak, a crag; a detached mass of rock, a boulder or large stone,” predates either of the singular words stone or rock. Stonerock, or stanrocces, as it was spelled, dates from the Early Old English, used from 600 to 950. I am not sure that this clarifies my quest but as is the norm for the OED, I got sucked into the many definitions and uses, which run to three pages for rock, including rock nosing, rockchuck, and rock-embosomed; and four and a half for stone, with such nifty combinations as stone harmonicon, stone-pock, and stone-toter.
Perhaps I could find a bit of clarity from on high. In the King James Bible, stone and rock seemed interchangeable, such as in Genesis 31:46, where we read of Jacob telling his brethren to “Gather stones; and they took stones, and made an heap.” (Now why they didn’t just say cairn here is beyond me!) But there are two situations where stone and rock cannot be substituted for one another. The first is the surprisingly common pastime (at least a dozen times) where somebody must “stone them/him/her with stones.” You can “stone them with rocks” but no matter how tin your ear is you cannot “rock them with rocks,” which allows for the introduction of this silly phrase: you can, at least since the 1960s, “rock them with The Stones.”
More common than death by stone is the affirmation of a Holy Being as the “rock of one’s salvation.” This sense highlights a central difference between the words. People often use rock to refer to something solid, large, grounded, substantial, something to base your faith upon, such as a mountain or palisade. No one would say the “stone of one’s salvation.” Stone, while connoting a hard mineral substance, favors smaller objects, such as something you can pick up in your hands, for example, the stones for the heap gathered by Jacob’s pals.
Seeking out an even higher authority I turned to Shakespeare. He also incorporated stone and rock into his writings, more than 115 times and 50 times, respectively (which includes the plural forms.) One of his most famous uses comes from As You Like It, in the banished Duke’s ode to a new forested life “And this our life exempt from public haunt/Finds tongues in trees, books in the running brooks,/Sermons in stones and good in every thing.” Clearly the Bard chose stone for the alliteration and sound, as he did in Titus Andronicus, where the title character states “A stone is soft as wax,—tribunes more hard than stones; A stone is silent, and offendeth not.” (One of my favorite poets, Robinson Jeffers, refers to the “insolent quietness of stone.”)
Shakespeare’s use of rock was often specific to the sea, as something to fear. “Rocks threaten us with wreck.” “And then there is the peril of waters, winds and rocks.” “Alas, the sea hath cast me on the rocks.” No one, especially one with Shakespeare’s gifts, would substitute stone in these situations. Again, his use of rock reflects the idea that rock refers to massive, immovable matter, though this idea does not limit rock to this definition.
I cannot end my consideration of these two terms without turning to one final source of inspiration, that of big time wrestling, or “rassling,” as one former National Park superintendent called it. I refer to the two icons of that theater, The Rock and Stone Cold Steve Austin. Surely these two men illustrate the differences between the two words.
Ultimately, I have concluded that there is some difference between the terms. I agree with Thorson that stone more often implies some sort of human use. Stone also does seem restricted to smaller material. But rock can also be used in these situations. In this sense all rocks are stones but not all stones are rocks. Clear as mud.
If you feel inclined to support a rock geek (and who wouldn’t be after reading such a lovely little post!), here’s a way to donate a buck or two or three to my “training to kick The Rock’s butt” fund. (Via Square) Thanks kindly for your support.
The Grand Canyon, an incision through layers of sedimentary rocks.
In geology, rock (or stone) is any naturally occurring solid mass or aggregate of minerals or mineraloid matter. It is categorized by the minerals included, its chemical composition, and the way in which it is formed. Rocks form the Earth's outer solid layer, the crust, and most of its interior, except for the liquid outer core and pockets of magma in the asthenosphere. The study of rocks involves multiple subdisciplines of geology, including petrology and mineralogy. It may be limited to rocks found on Earth, or it may include planetary geology that studies the rocks of other celestial objects.
Rocks are usually grouped into three main groups: igneous rocks, sedimentary rocks and metamorphic rocks. Igneous rocks are formed when magma cools in the Earth's crust, or lava cools on the ground surface or the seabed. Sedimentary rocks are formed by diagenesis and lithification of sediments, which in turn are formed by the weathering, transport, and deposition of existing rocks. Metamorphic rocks are formed when existing rocks are subjected to such high pressures and temperatures that they are transformed without significant melting.
Humanity has made use of rocks since the earliest humans. This early period, called the Stone Age, saw the development of many stone tools. Stone was then used as a major component in the construction of buildings and early infrastructure. Mining developed to extract rocks from the Earth and obtain the minerals within them, including metals. Modern technology has allowed the development of new man-made rocks and rock-like substances, such as concrete.
Study
Geology is the study of Earth and its components, including the study of rock formations. Petrology is the study of the character and origin of rocks. Mineralogy is the study of the mineral components that create rocks. The study of rocks and their components has contributed to the geological understanding of Earth's history, the archaeological understanding of human history, and the development of engineering and technology in human society.[1]
While the history of geology includes many theories of rocks and their origins that have persisted throughout human history, the study of rocks was developed as a formal science during the 19th century. Plutonism was developed as a theory during this time, and the discovery of radioactive decay in 1896 allowed for the radiocarbon dating of rocks. Understanding of plate tectonics developed in the second half of the 20th century.[2]
Classification
Rocks are composed primarily of grains of minerals, which are crystalline solids formed from atoms chemically bonded into an orderly structure.[4]: 3 Some rocks also contain mineraloids, which are rigid, mineral-like substances, such as volcanic glass,[5]: 55, 79 that lacks crystalline structure. The types and abundance of minerals in a rock are determined by the manner in which it was formed.
Most rocks contain silicate minerals, compounds that include silica tetrahedra in their crystal lattice, and account for about one-third of all known mineral species and about 95% of the earth's crust.[6] The proportion of silica in rocks and minerals is a major factor in determining their names and properties.[7]
Rock outcrop along a mountain creek near Orosí, Costa Rica.Rocks are classified according to characteristics such as mineral and chemical composition, permeability, texture of the constituent particles, and particle size. These physical properties are the result of the processes that formed the rocks.[5] Over the course of time, rocks can be transformed from one type into another, as described by a geological model called the rock cycle. This transformation produces three general classes of rock: igneous, sedimentary and metamorphic.
Those three classes are subdivided into many groups. There are, however, no hard-and-fast boundaries between allied rocks. By increase or decrease in the proportions of their minerals, they pass through gradations from one to the other; the distinctive structures of one kind of rock may thus be traced, gradually merging into those of another. Hence the definitions adopted in rock names simply correspond to selected points in a continuously graduated series.[8]
Igneous rock
Sample of igneous gabbroIgneous rock (derived from the Latin word igneus, meaning of fire, from ignis meaning fire)[9] is formed through the cooling and solidification of magma or lava. This magma may be derived from partial melts of pre-existing rocks in either a planet's mantle or crust. Typically, the melting of rocks is caused by one or more of three processes: an increase in temperature, a decrease in pressure, or a change in composition.[10]: 591–599
Igneous rocks are divided into two main categories:
Magmas tend to become richer in silica as they rise towards the Earth's surface, a process called magma differentiation. This occurs both because minerals low in silica crystallize out of the magma as it begins to cool (Bowen's reaction series) and because the magma assimilates some of the crustal rock through which it ascends (country rock), and crustal rock tends to be high in silica. Silica content is thus the most important chemical criterion for classifying igneous rock.[7] The content of alkali metal oxides is next in importance.[11]
About 65% of the Earth's crust by volume consists of igneous rocks. Of these, 66% are basalt and gabbro, 16% are granite, and 17% granodiorite and diorite. Only 0.6% are syenite and 0.3% are ultramafic. The oceanic crust is 99% basalt, which is an igneous rock of mafic composition. Granite and similar rocks, known as granitoids, dominate the continental crust.[12][13]
Sedimentary rock
Sedimentary rocks are formed at the earth's surface by the accumulation and cementation of fragments of earlier rocks, minerals, and organisms[14] or as chemical precipitates and organic growths in water (sedimentation). This process causes clastic sediments (pieces of rock) or organic particles (detritus) to settle and accumulate or for minerals to chemically precipitate (evaporite) from a solution. The particulate matter then undergoes compaction and cementation at moderate temperatures and pressures (diagenesis).[5]: 265–280 [15]: 147–154
Before being deposited, sediments are formed by weathering of earlier rocks by erosion in a source area and then transported to the place of deposition by water, wind, ice, mass movement or glaciers (agents of denudation).[5] About 7.9% of the crust by volume is composed of sedimentary rocks, with 82% of those being shales, while the remainder consists of 6% limestone and 12% sandstone and arkoses.[13] Sedimentary rocks often contain fossils. Sedimentary rocks form under the influence of gravity and typically are deposited in horizontal or near horizontal layers or strata, and may be referred to as stratified rocks.[16]
Sediment and the particles of clastic sedimentary rocks can be further classified by grain size. The smallest sediments are clay, followed by silt, sand, and gravel. Some systems include cobbles and boulders as measurements.[17]
Metamorphic rock
Metamorphic banded gneissMetamorphic rocks are formed by subjecting any rock type—sedimentary rock, igneous rock or another older metamorphic rock—to different temperature and pressure conditions than those in which the original rock was formed. This process is called metamorphism, meaning to "change in form". The result is a profound change in physical properties and chemistry of the stone. The original rock, known as the protolith, transforms into other mineral types or other forms of the same minerals, by recrystallization.[5] The temperatures and pressures required for this process are always higher than those found at the Earth's surface: temperatures greater than 150 to 200 °C and pressures greater than 1500 bars.[18] This occurs, for example, when continental plates collide.[19]: 31–33, 134–139 Metamorphic rocks compose 27.4% of the crust by volume.[13]
The three major classes of metamorphic rock are based upon the formation mechanism. An intrusion of magma that heats the surrounding rock causes contact metamorphism—a temperature-dominated transformation. Pressure metamorphism occurs when sediments are buried deep under the ground; pressure is dominant, and temperature plays a smaller role. This is termed burial metamorphism, and it can result in rocks such as jade. Where both heat and pressure play a role, the mechanism is termed regional metamorphism. This is typically found in mountain-building regions.[7]
Depending on the structure, metamorphic rocks are divided into two general categories. Those that possess a texture are referred to as foliated; the remainders are termed non-foliated. The name of the rock is then determined based on the types of minerals present. Schists are foliated rocks that are primarily composed of lamellar minerals such as micas. A gneiss has visible bands of differing lightness, with a common example being the granite gneiss. Other varieties of foliated rock include slates, phyllites, and mylonite. Familiar examples of non-foliated metamorphic rocks include marble, soapstone, and serpentine. This branch contains quartzite—a metamorphosed form of sandstone—and hornfels.[7]
Extraterrestrial rocks
Though most understanding of rocks comes from those of Earth, rocks make up many of the universe's celestial bodies. In the Solar System, Mars, Venus, and Mercury are composed of rock, as are many natural satellites, asteroids, and meteoroids. Meteorites that fall to Earth provide evidence of extraterrestrial rocks and their composition. They are typically heavier than rocks on Earth. Asteroid rocks can also be brought to Earth through space missions, such as the Hayabusa mission.[20] Lunar rocks and Martian rocks have also been studied.[21]
Human use
Ceremonial cairn of rocks, an ovoo, from MongoliaThe use of rock has had a huge impact on the cultural and technological development of the human race. Rock has been used by humans and other hominids for at least 2.5 million years.[22] Lithic technology marks some of the oldest and continuously used technologies. The mining of rock for its metal content has been one of the most important factors of human advancement, and has progressed at different rates in different places, in part because of the kind of metals available from the rock of a region.
Anthropic rock
Anthropic rock is synthetic or restructured rock formed by human activity. Concrete is recognized as a human-made rock constituted of natural and processed rock and having been developed since Ancient Rome.[23] Rock can also be modified with other substances to develop new forms, such as epoxy granite.[24] Artificial stone has also been developed, such as Coade stone.[25] Geologist James R. Underwood has proposed anthropic rock as a fourth class of rocks alongside igneous, sedimentary, and metamorphic.[26]
Building
A stonehouse on the hill in Sastamala, FinlandRock varies greatly in strength, from quartzites having a tensile strength in excess of 300 MPa[27] to sedimentary rock so soft it can be crumbled with bare fingers (that is, it is friable).[28] (For comparison, structural steel has a tensile strength of around 350 MPa.[29]) Relatively soft, easily worked sedimentary rock was quarried for construction as early as 4000 BCE in Egypt,[30] and stone was used to build fortifications in Inner Mongolia as early as 2800 BCE.[31] The soft rock, tuff, is common in Italy, and the Romans used it for many buildings and bridges.[32] Limestone was widely used in construction in the Middle Ages in Europe [33] and remained popular into the 20th century.[34]
Mining
Mining is the extraction of valuable minerals or other geological materials from the earth, from an ore body, vein or seam.[35] The term also includes the removal of soil. Materials recovered by mining include base metals, precious metals, iron, uranium, coal, diamonds, limestone, oil shale, rock salt, potash, construction aggregate and dimension stone. Mining is required to obtain any material that cannot be grown through agricultural processes, or created artificially in a laboratory or factory. Mining in a wider sense comprises extraction of any resource (e.g. petroleum, natural gas, salt or even water) from the earth.[36]
Mining of rock and metals has been done since prehistoric times. Modern mining processes involve prospecting for mineral deposits, analysis of the profit potential of a proposed mine, extraction of the desired materials, and finally reclamation of the land to prepare it for other uses once mining ceases.[37]
Mining processes may create negative impacts on the environment both during the mining operations and for years after mining has ceased. These potential impacts have led to most of the world's nations adopting regulations to manage negative effects of mining operations.[38]
Stone tools have been used for millions of years by humans and earlier hominids. The Stone Age was a period of widespread stone tool usage.[39] Early Stone Age tools were simple implements, such as hammerstones and sharp flakes. Middle Stone Age tools featured sharpened points to be used as projectile points, awls, or scrapers. Late Stone Age tools were developed with craftsmanship and distinct cultural identities.[40] Stone tools were largely superseded by copper and bronze tools following the development of metallurgy.
See also
References