The Collaborative International Dictionary of English v.0.48:

Pyrites \Py*ri"tes\, n. [L., fr. Gr. ?, fr. ? fire. See Pyre.]
   (Min.)
   A name given to a number of metallic minerals, sulphides of
   iron, copper, cobalt, nickel, and tin, of a white or
   yellowish color.
   [1913 Webster]

   Note: The term was originally applied to the mineral pyrite,
         or iron pyrites, in allusion to its giving sparks when
         struck with steel.
         [1913 Webster]

   Arsenical pyrites, arsenopyrite.

   Auriferous pyrites. See under Auriferous.

   Capillary pyrites, millerite.

   Common pyrites, isometric iron disulphide; pyrite.

   Hair pyrites, millerite.

   Iron pyrites. See Pyrite.

   Magnetic pyrites, pyrrhotite.

   Tin pyrites, stannite.

   White iron pyrites, orthorhombic iron disulphide;
      marcasite. This includes cockscomb pyrites (a variety of
      marcasite, named in allusion to its form), spear pyrites,
      etc.

   Yellow pyrites, or Copper pyrites, the sulphide of copper
      and iron; chalcopyrite.
      [1913 Webster] Pyritic

The Collaborative International Dictionary of English v.0.48:

Magnetic \Mag*net"ic\, Magnetical \Mag*net"ic*al\, a. [L.
   magneticus: cf. F. magn['e]tique.]
   1. Pertaining to the magnet; possessing the properties of the
      magnet, or corresponding properties; as, a magnetic bar of
      iron; a magnetic needle.
      [1913 Webster]

   2. Of or pertaining to, or characterized by, the earth's
      magnetism; as, the magnetic north; the magnetic meridian.
      [1913 Webster]

   3. Capable of becoming a magnet; susceptible to magnetism;
      as, the magnetic metals.
      [1913 Webster]

   4. Endowed with extraordinary personal power to excite the
      feelings and to win the affections; attractive; inducing
      attachment.
      [1913 Webster]

            She that had all magnetic force alone. --Donne.
      [1913 Webster]

   5. Having, susceptible to, or induced by, animal magnetism,
      so called; hypnotic; as, a magnetic sleep. See
      Magnetism. [Archaic]
      [1913 Webster +PJC]

   Magnetic amplitude, attraction, dip, induction, etc.
      See under Amplitude, Attraction, etc.

   Magnetic battery, a combination of bar or horseshoe magnets
      with the like poles adjacent, so as to act together with
      great power.

   Magnetic compensator, a contrivance connected with a ship's
      compass for compensating or neutralizing the effect of the
      iron of the ship upon the needle.

   Magnetic curves, curves indicating lines of magnetic force,
      as in the arrangement of iron filings between the poles of
      a powerful magnet.

   Magnetic elements.
      (a) (Chem. Physics) Those elements, as iron, nickel,
          cobalt, chromium, manganese, etc., which are capable
          or becoming magnetic.
      (b) (Physics) In respect to terrestrial magnetism, the
          declination, inclination, and intensity.
      (c) See under Element.

   Magnetic fluid, the hypothetical fluid whose existence was
      formerly assumed in the explanations of the phenomena of
      magnetism; -- no longer considered a meaningful concept.


   Magnetic iron, or Magnetic iron ore. (Min.) Same as
      Magnetite.

   Magnetic needle, a slender bar of steel, magnetized and
      suspended at its center on a sharp-pointed pivot, or by a
      delicate fiber, so that it may take freely the direction
      of the magnetic meridian. It constitutes the essential
      part of a compass, such as the mariner's and the
      surveyor's.

   Magnetic poles, the two points in the opposite polar
      regions of the earth at which the direction of the dipping
      needle is vertical.

   Magnetic pyrites. See Pyrrhotite.

   Magnetic storm (Terrestrial Physics), a disturbance of the
      earth's magnetic force characterized by great and sudden
      changes.

   magnetic tape (Electronics), a ribbon of plastic material
      to which is affixed a thin layer of powder of a material
      which can be magnetized, such as ferrite. Such tapes are
      used in various electronic devices to record fluctuating
      voltages, which can be used to represent sounds, images,
      or binary data. Devices such as audio casette recorders,
      videocasette recorders, and computer data storage devices
      use magnetic tape as an inexpensive medium to store data.
      Different magnetically susceptible materials are used in
      such tapes.

   Magnetic telegraph, a telegraph acting by means of a
      magnet. See Telegraph.
      [1913 Webster + PJC]

The Collaborative International Dictionary of English v.0.48:

Pyrrhotine \Pyr"rho*tine\, Pyrrhotite \Pyr"rho*tite\, n. [Gr. ?
   flame-colored, fr. ? fire.] (Min.)
   A bronze-colored mineral, of metallic luster. It is a
   sulphide of iron, and is remarkable for being attracted by
   the magnet. Called also magnetic pyrites.
   [1913 Webster] pyrrol

WordNet (r) 3.0 (2006):

magnetic pyrites
    n 1: a brownish iron sulfide mineral (FeS) having weak magnetic
         properties [syn: pyrrhotite, pyrrhotine, magnetic
         pyrites]