Application of Forensic Chemistry

I found a a paper entitled "The forensic analysis of soils and sediment taken from the cast of a footprint", this paper explains how crime investigators could use the forensic chemistry method (EDTA) to determine whether the limestime took from a criminal shoes came from the crime scene. However, it does not explain the limitation of the methods i.e. EDTA and AAS. Therefore I have formulated the following question, I think I know how to answer. However, I would like to know if you could give a better answer.

Questions:

You work for a crime investigator. The police have found that a dead person found at Bedford road had limestone minerals at his shoes

1. How did you establish whether or not it limestone (calcium carbonate minerla)?

2. Suppose you limestone has the following impurities (Zn: 3+/- 0.5 mg/kg and Fe 326 +/- 15 mg/kg). How can you find out if the dead person have strolled down at the park or had previously been in a limestone quarry in Aberdeenshire?

3. If the limestone from Aberdeenshire has Zn concentration of 7 +/- 0.1mg/kg and Fe from 300 +/- 10 mg/kg, could you exclude whether the dead person has been at the quarry or not?