A process for reducing rocks and concentrating heavy minerals

Open-File Report 2016-1022
By:  and 



To obtain minerals suitable for age-dating and other analyses, it is necessary to first reduce the mineral-bearing rock to a fine, sand-like consistency. Reducing whole rock requires crushing, grinding, and sieving. Ideally, the reduced material should range in size from 80- to 270-mesh (an opening between wires in a sieve). The openings in an 80-mesh sieve are equal to 0.007 inches, 0.177 millimeters, or 177 micrometers. This size range ensures that compound grains are mostly disaggregated and that grains, in general, are dimensionally similar. This range also improves the segregation rate of conspicuous to extremely small individual heavy mineral grains.

Once the rock is reduced to grains, it is necessary to separate the grains into paramagnetic and nonparamagnetic and heavy and light mineral fractions. In separating grains by property, those minerals chemically suited for radiometric dating are abundantly concentrated. Grams of mineralogical material can then be analyzed and characterized by multiple methods including trace element chemistry, laser ablation, and in particular, ion geochronology.

Suggested Citation

Strong, T.R., and Driscoll, R.L., 2016, A process for reducing rocks and concentrating heavy minerals: U.S. Geological Survey Open-File Report 2016–1022, 16 p., http://dx.doi.org/10.3133/ofr20161022.

ISSN: 2331-1258 (online)

ISSN: 0196-1497 (print)

Table of Contents

  • Abstract
  • Introduction
  • Preparation for Rock Reduction
  • Sturtevant Jaw Crusher General Information
  • Sturtevant Jaw Crusher Setup
  • Sturtevant Jaw Crusher Procedure
  • Bico-Braun Vertical Disk Grinder-Pulverizer General Information
  • Bico-Braun Vertical Disk Grinder-Pulverizer Setup
  • Bico-Braun Vertical Disk Grinder-Pulverizer Procedure
  • Tyler Ro-Tap Test Sieve Shaker General Information
  • Tyler Ro-Tap Test Sieve Shaker Setup
  • Tyler Ro-Tap Test Sieve Shaker Procedure
  • Wilfley Table General Information
  • Wilfley Table Setup
  • Wilfley Table Procedure
  • Frantz Magnetic Separation
  • Frantz Magnetic Separation General Introduction
  • Frantz Magnetic Separator Setup
  • Frantz Magnetic Separator Procedure
  • Heavy Liquids General Information
  • Heavy Liquids Separation Setup
  • Heavy Liquid Separation Procedure
  • Conclusions
  • References Cited
Publication type Report
Publication Subtype USGS Numbered Series
Title A process for reducing rocks and concentrating heavy minerals
Series title Open-File Report
Series number 2016-1022
DOI 10.3133/ofr20161022
Year Published 2016
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Central Mineral and Environmental Resources Science Center
Description iv, 16 p.
Online Only (Y/N) N
Additional Online Files (Y/N) N
Google Analytic Metrics Metrics page
Additional publication details