What is "replaced crystal"

Replace \Re*place"\ (r?-pl?s"), v. t. [Pref. re- + place: cf. F. replacer.]

1. To place again; to restore to a former place, position, condition, or the like.

   The earl . . . was replaced in his government.
   --Bacon.

2. To refund; to repay; to restore; as, to replace a sum of money borrowed.

3. To supply or substitute an equivalent for; as, to replace a lost document.

   With Israel, religion replaced morality.
   --M. Arnold.

4. To take the place of; to supply the want of; to fulfull the end or office of.

   This duty of right intention does not replace or supersede the duty of consideration.
   --Whewell.

5. To put in a new or different place.

   Note: The propriety of the use of replace instead of displace, supersede, take the place of, as in the third and fourth definitions, is often disputed on account of etymological discrepancy; but the use has been sanctioned by the practice of careful writers.

   Replaced crystal (Crystallog.), a crystal having one or more planes in the place of its edges or angles.