A uranium-lead age determined from a zircon crystal removed from ...

[altibaby]

A uranium-lead age determined from a zircon crystal removed from a sandstone would reflect the time elapsed since the ________ of the zircon.
 
  A) erosion
  B) deposition
  C) crystallization
  D) cementation

Question 2

In order to use a radioactive-decay scheme to calculate the age of a mineral all of the following conditions must be met except
 
  A) the half-life must be known.
  B) no daughter isotope present prior to the start of parental decay or the amount of daughter can be determined.
  C) no parent or daughter isotopes can be gained or lost from the mineral once decay starts.
  D) only one radioactive isotope can exist in the rock so that cross-decay doesn't occur.

[JaynaD87]

Answer to Question 1

Answer: C

Answer to Question 2

Answer: D