See also:corundum, much used as an abrasive
See also:agent . It was known to the Greeks under the name of vµbptr or vµipts, which is defined by Dioscorides as a
See also:stone used in
See also:engraving . The
See also:Hebrew word shamir (related to the
See also:Egyptian asmir), where translated in our versions of the Old Testament " adamant " and "
See also:diamond," probably signified the
See also:emery-stone or corundum . Emery occurs as a granular or massive, dark-coloured, dense substance, having much the appearance of an iron-ore . Its specific gravity varies with its composition from 3'7 to 4.3 . Under the microscope, it is seen to be a
See also:mechanical aggregate of corundum, usually in grains or minute crystals of a bluish
See also:colour, with
See also:magnetite, which also is granular and crystalline . Other iron oxides, like
See also:haematite and
See also:limonite, may be
See also:present as alteration-products of the magnetite . Some of the alumina and iron
See also:oxide may occasionally be chemically combined, so as to
See also:form an iron
See also:spinel, or hercynite . In addition to these minerals emery sometimes contains
See also:tourmaline, cassiterite, &c . Indeed emery may be regarded as a
See also:rock rather than a definite
See also:species . The hardness of emery is about 8, whereas that of pure corundum is 9 . The " abrasive power," or " effective hardness," of emery is by no means proportional to the amount of alumina which it contains, but seems rather to depend on its
See also:condition .
Thus, taking the effective hardness of
See also:sapphire as Iota, Dr J .
See also:Smith found that the emery of
See also:Samos with 70.10% of alumina had a corresponding hardness of 56; that of
See also:Naxos, with 68.53 of Al203, a hardness of 46; and that of Gumach with 77.82 of Al203, a hardness of 47 . Emery has been worked from a very remote
See also:period in the Isle of Naxos, one of the
See also:Cyclades, whence the stone was called naxium by Pliny and other
See also:Roman writers . The mineral occurs as loose blocks and as lenticular masses or irregular beds in granular
See also:limestone, associated with crystalline
See also:schists . The Naxos emery has been described by
See also:Professor G . Tschermak . From a chemical analysis of a sample it has been calculated that the emery contained 52.4% of corundum, 32.1 of magnetite, 11'5 of tourmaline, 2 of
See also:muscovite and 2 of margarite . Important deposits of corundum were discovered in
See also:Asia Minor by J . Lawrence Smith, when investigating
See also:Turkish mineral resources about 1847 . The chief
See also:sources of emery there are Gumach Dagh, a
See also:mountain about 12 M . E. of Ephesus; Kula, near
See also:Ala-shehr; and the mines in the hills between Thyra and Cosbonnar, south of
See also:Smyrna . The occurrence is similar to that in Naxos .
The emery is found as detached blocks in a reddish
See also:soil, and as rounded masses embedded in a crystalline limestone associated with mica-schist,
See also:gneiss and granite . The proportion of corundum in this emery is said to vary from 37 to 57% . Emery is worked at several localities in the
See also:United States, especially near Chester, in
See also:county, Mass., where it is associated with peridotites . The corundum and magnetite are regarded by Dr J . H .
See also:Pratt as basic segregations from an igneous magma . The deposits were discovered by H . S . Lucas in 1864 . The hardness and toughness of emery render it difficult to
See also:work, but it may be extracted from the rock by
See also:blasting in holes bored with diamond drills . In the East
See also:fire-setting is employed . The emery after being broken up is carefully picked by
See also:hand, and then ground or stamped, and separated into grades by
See also:sieves .
The higher grades are prepared by washing and eleutriation, the finest being known as "
See also:flour of emery." A very
See also:fine emery dust is collected in the stamping
See also:room, where it is deposited after floating in the air . The fine powder is used by lapidaries and
See also:glass manufacturers . Emery-wheels are made by consolidating the powdered mineral with an agglutinating
See also:medium like shellac or silicate of soda or vulcanized india-
See also:rubber . Such wheels are not only used by dentists and lapidaries but are employed on a large scale in mechanical workshops for grinding, shaping and polishing
See also:steel . Emery-sticks, emery-
See also:cloth and emery-paper are made by coating the several materials with powdered emery mixed with glue, or other adhesive
See also:media . (See CORUNDUM.) (F . W . R .
WILLIAM EMERSON (1701-1782)
EMETICS (from Gr. inerucos, causing vomit)
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