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Topic: Hardness

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	Mineral Hardness
		Hardness is measured by the resistance which a smooth surface offers to abrasion.
		The degree of hardness is determined by observing the comparative ease or difficulty which which one mineral is scratched by another.
		The selection of mineral species for hardness standards is based on the common availability of the mineral.
	webmineral.com /help/Hardness.shtml (171 words)

	Hardness
		Hardness is a measure of dissolved mineral salts, mainly calcium and magnesium carbonates, in water.
		Hardness has a direct affect on the cellular functions of fish, plants and microorganisms and although fish from hard water areas do not seem to suffer from softer than natural conditions the reverse does not apply.
		Hardness is expressed in degrees but the units differ form country to country and test kit measurements vary depending on whether total hardness or carbonate hardness is being determined.
	www.thatfishshop.com /chemistry/hardness.htm (654 words)

	Hardness - Wikipedia, the free encyclopedia
		In materials science, hardness is the characteristic of a solid material expressing its resistance to permanent deformation.
		Scratch hardness is usually measured on the Mohs scale of mineral hardness.
		One scale that measures rebound hardness is the Bennett Hardness Scale.
	en.wikipedia.org /wiki/Hardness (459 words)

	Maine Health and Environmental Testing Lab - Hardness
		Hardness is caused by minerals, primarily calcium and magnesium, which are picked up by water passing through underground mineral deposits.
		Hard water is not considered contaminated, but it does retard the cleaning action of soap and forms a scale on cooking utensils, hot water pipes and heaters.
		Hardness is the total concentration of calcium and magnesium in water.
	www.maine.gov /dhs/etl/hardness.htm (191 words)

	hardness. The Columbia Encyclopedia, Sixth Edition. 2001-05
		Hardness may differ with the direction of the scratch made on the substance.
		The hardness numeral of the Brinell scale is based upon the indentation produced when pressure is exerted by a sphere on the substance.
		The hardness of a material may be modified by the presence of small quantities of another substance, as in metallic alloys, or by impurities in minerals.
	www.bartleby.com /65/ha/hardness.html (325 words)

	Mohs scale of mineral hardness - Wikipedia, the free encyclopedia
		It was created, in 1812, by the German mineralogist Friedrich Mohs and is one of several definitions of hardness in materials science.
		The hardness of a material is measured against the scale by finding the hardest material that the given material can scratch, and/or the softest material that can scratch the given material.
		Mohs' is a purely ordinal scale with, for example, corundum being twice as hard as topaz, but diamond, almost four times as hard as corundum.
	en.wikipedia.org /wiki/Mohs_hardness_scale (310 words)

	Maine Health and Environmental Testing Lab - Hardness
		Hardness is caused by minerals, primarily calcium and magnesium, which are picked up by water passing through underground mineral deposits.
		Hard water is not considered contaminated, but it does retard the cleaning action of soap and forms a scale on cooking utensils, hot water pipes and heaters.
		Hardness is the total concentration of calcium and magnesium in water.
	www.state.me.us /dhhs/etl/hardness.htm (191 words)

	Testing for hardness with Mohs scale
		The hardness of a mineral is an easy diagnostic tests to perform in the attempt to identify an unknown mineral.
		A scale to measure hardness was devised by Austrian mineralogist Frederick (Friedrich) Mohs in 1822, and is currently the standard scale for measuring hardness.
		Fluorite at 4 is not twice as hard as gypsum at 2; nor is the difference between calcite and fluorite similar to the difference between corundum and diamond.
	www.inlandlapidary.com /user_area/hardness.asp (669 words)

	Hardness
		The hardness is calculated by dividing the load by the area of the curved surface of the indention, (the area of a hemispherical surface is arrived at by multiplying the square of the diameter by 3.14159 and then dividing by 2).
		Shore hardness [15] is a measure of the resistance of material to indentation by 3 spring-loaded indenter.
		The Mohs hardness [19] of a mineral is determined by observing whether its surface is scratched by a substance of known or defined hardness.
	www.calce.umd.edu /general/Facilities/Hardness_ad_.htm (5414 words)

	Mineral Resources: Hardness
		Hardness is defined by how well a substance will resist scratching by another substance.
		A scale to measure hardness was devised by Austrian mineralogist Frederick (Friedrich) Mohs in 1822, and is currently the standard scale for measuring hardness.
		Hardness testing is done by "swiping" one mineral with the other.
	www.minerals.net /resource/property/hardness.htm (916 words)

	Hardness - Water Contaminates - Aquapure Filters
		Hard water is found over 80% of the United States.
		The hardness of a water supply is determined by the content of calcium and magnesium salts.
		Water having a hardness content less than 0.6 gpg is considered commercially soft.
	www.aquapurefilters.com /contaminates/136/hardness.html (340 words)

	Diamonds \| American Museum of Natural History
		Hardness is the measure of a substance's resistance to being scratched, and only a diamond can scratch another diamond.
		When the mineral hardness numbers from the Mohs scale are plotted against those on the more quantitative Knoop scale (based on the force needed to make indentations using a diamond), we can see how it doesn't adequately express the extreme hardness of diamond.
		It is in fact difficult to measure the hardness of diamond, because diamond must be used to measure its own hardness.
	www.amnh.org /exhibitions/diamonds/hardness.html (149 words)

	Hardness Testers Metal Non Metal Concrete Coating
		Elcometer 3030 and 3040 Persoz and König Pendulum Hardness Testers
		The Elcometer 3095 Buchholz Hardness Tester is used for measuring the hardness of a coating by indentation of a bevelled disc indenting tool with a sharp edge.
		The length of the trace is inversely proportional to the hardness.
	www.bamr.co.za /hardness.shtml (1345 words)

	Application by Test Type - Hardness (Site not responding. Last check: )
		Hardness is, however, used extensively to characterize materials and to determine if they are suitable for their intended use.
		All of the hardness tests described in this section involve the use of a specifically shaped indenter, significantly harder than the test sample, that is pressed into the surface of the sample using a specific force.
		The hardness values are determined by measuring either the depth of indenter penetration or the size of the resultant indent.
	www.instron.us /wa/applications/test_types/hardness (378 words)

	Drinking Water Hard Water Hardness Calcium Magnesium Scale Stained Laundry
		Hard water is not a health risk, but a nuisance because of mineral buildup on fixtures and poor soap and/or detergent performance.
		Hard water is not a health hazard, but dealing with hard water in the home can be a nuisance.
		The hardness (calcium and magnesium concentration) of water can be approximated with a home-use water testing kit, or can be measured more accurately with a laboratory water test.
	www.water-research.net /hardness.htm (1543 words)

	Hardness
		Hardness measurements are widely used for the quality control of materials because they are quick and considered to be nondestructive tests when the marks or indentations produced by the test are in low stress areas.
		Mohs hardness test, while greatly facilitating the identification of minerals in the field, is not suitable for accurately gauging the hardness of industrial materials such as steel or ceramics.
		The Barcol hardness test method is used to determine the hardness of both reinforced and non-reinforced rigid plastics and to determine the degree of cure of resins and plastics.
	www.ndt-ed.org /EducationResources/CommunityCollege/Materials/Mechanical/Hardness.htm (1743 words)

	Mohs scale of mineral hardness Summary
		At the lower, softer end of the scale, the difference in hardness is close to linear, but at the extremes of harness, there are much greater increases in absolute hardness (e.g., a greater increase in the hardness between corundum and diamond than between quartz and topaz).
		Hardness is a property of minerals derived from the nature and strength of chemical bonds in and between crystals.
		Hardness characteristics—especially in calcite crystals—may vary as a property dependent upon the direction of the scratch (i.e., able show evidence of a particular Mohs'; number if scratched along one face or direction as opposed to a different hardness number if scratched in a different direction).
	www.bookrags.com /Mohs_scale_of_mineral_hardness (732 words)

	Rockwell Hardness - Materials Evaluation and Engineering, Inc.
		Rockwell hardness testing is a general method for measuring the bulk hardness of metallic and polymer materials.
		Hardness testing is widely used for material evaluation due to its simplicity and low cost relative to direct measurement of many properties.
		A Rockwell hardness number is calculated from the depth of permanent deformation of the sample after application and removal of the test load.
	www.mee-inc.com /rockhar.html (438 words)

	Hardness Definitions
		Hardness: the resistance of a smooth surface to scratching or abrassion.
		Therefore, hardness is the measure of the material's ability to resist scratches or abrassions.
		The Mohs hardness of a mineral is determined by observing whether its surface is scratched by a substance of known or defined hardness.
	www.waldaninternational.com /hardnessDef.shtml (890 words)

	Hardness Testing
		Hardness is the property of a material that enables it to resist plastic deformation, usually by penetration.
		Hardness is not an intrinsic material property dictated by precise definitions in terms of fundamental units of mass, length and time.
		The usual method to achieve a hardness value is to measure the depth or area of an indentation left by an indenter of a specific shape, with a specific force applied for a specific time.
	gordonengland.co.uk /hardness (540 words)

	Hardness Definitions
		Hardness: the resistance of a smooth surface to scratching or abrassion.
		Therefore, hardness is the measure of the material's ability to resist scratches or abrassions.
		The Mohs hardness of a mineral is determined by observing whether its surface is scratched by a substance of known or defined hardness.
	waldaninternational.com /hardnessDef.shtml (890 words)

	SN Pencil Hardness Feature
		Hardness is a measure of the cure of the film or how the coating has softened when in contact with various liquids.
		Hardness, as we understand it here, is the capacity of a given surface to resist scratching, marring or gouging.
		The process is started with the hardest pencil and continued down the scale of hardness to either of two end points; one, the pencil that will not cut into or gouge the film (pencil hardness), or two, the pencil that will not scratch the film (scratch hardness).
	www.astm.org /SNEWS/SEPTEMBER_2002/guevin_sept02.html (1182 words)

	Water Chemistry
		Water hardness is of interest to aquarists for two reasons: to provide the proper environment for the fish and to help stabilize the pH in the aquarium.
		General hardness is primarily the measure of calcium (Ca++) and magnesium (Mg++) ions in the water.
		Carbonate hardness (KH) is the measure of bicarbonate (HCO3-) and carbonate (CO3--) ions in the water.
	aquaticconcepts.thekrib.com /Articles/Water_Chemistry.htm (1616 words)

	Mineral Gallery: Hardness
		Hardness is one measure of the strength of the structure of the mineral relative to the strength of its chemical bonds.
		Meaning that fluorite at 4 is not twice as hard as gypsum at 2; nor is the difference between calcite and fluorite similar to the difference between corundum and diamond.
		Keep in mind that most minerals have small differences in hardness according to the direction of the scratch and the orientation of the scratch and that some minerals such as kyanite and diamond, have a marked difference in hardness with respect to these factors.
	mineral.galleries.com /minerals/property/hardness.htm (1028 words)

	Moh's scale - microhardness
		It is true that obtaining an estimation of the hardness of the minerals in the Mohs scale, using; one of the standard hardness testers, is mainly of academic interest.
		It is to be noted that the average hardness of talc on the cleavage surface first studied is represented by a microhardness of approximately 1, while the average readings on the vertical cross sections gave a microhardness of 20 and 21.5.
		In selenite, the hardness on the clinopinacoid, pyramid and prism planes, i.e., {010}, {111}, and {110} planes respectively, were studied by means of microcuts in various directions.
	www.minsocam.org /MSA/collectors_corner/arc/microhardness.htm (1896 words)

	- Water Hardness (Site not responding. Last check: )
		The so-called 'hardness' of water has a significant meaning for the life of the aquarium inhabitants.
		On the other hand the proper development of reproduction and vitality of fish requires a certain rate of hardness; it should be the same or similar to the one in the native basin of every single fish kind.
		The water hardness is measured in so-called 'milligramequals' or in Ca or Mg mols per 1 liter of water.
	library.thinkquest.org /C0124402/data/html/5/5waterhardness.htm (482 words)

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