# Specific gravity and density test

Canonical page: https://lithomap.app/resources/field-tests/specific-gravity-density-test
Last reviewed: September 18, 2026
Page purpose: Original LithoMap field-method reference for human readers, search systems, and language models.

## Direct answer

For a solid, nonporous specimen, divide its dry mass by the apparent loss of mass when it is fully submerged in water without touching the container. The result approximates specific gravity when both measurements use the same mass units.

## Why the test works

Specific gravity compares a material’s density with water. In a hydrostatic test, the difference between dry and submerged weight corresponds to the displaced water volume.

The method works best on a single compact specimen. Pores, attached matrix, multiple minerals, trapped air, absorbent material, and water-soluble minerals can shift the result substantially.

## Field kit

- Digital scale with suitable precision and capacity
- Cup of clean water
- Thin thread or wire sling that does not absorb water
- Support that holds the specimen clear of the cup
- Towel and notebook

## Procedure

1. Screen the specimen: Do not immerse porous, crumbly, water-soluble, reactive, valuable, treated, contaminated, or unknown hazardous material.
2. Measure dry mass: Tare the scale, weigh the dry specimen, and record the units and precision.
3. Prepare suspension: Tare the scale with the water container and empty sling arranged exactly as they will be used.
4. Measure while submerged: Suspend the specimen completely under water without touching the bottom or sides. Remove visible bubbles and record the stable reading.
5. Calculate and repeat: Divide dry mass by dry mass minus submerged apparent mass. Repeat the measurement; disagreement signals bubbles, contact, absorption, or insufficient scale precision.

## Interpreting results

- Near 2.6 to 2.8: Common among quartz, feldspar, calcite, and many ordinary silicate or carbonate materials; the value alone is not distinctive.
- Near 4 to 5: Noticeably dense minerals such as barite, some iron oxides, and several sulfides become plausible; use streak, hardness, cleavage, and safety context.
- Above roughly 7: Very dense native metals or lead-rich minerals may be possible, but mixtures and measurement error must be excluded.
- Repeated values differ substantially: The specimen or setup is unsuitable: check bubbles, water absorption, contact, thread tare, scale precision, and mixed composition.

## Examples and related guides

- Quartz: Specific gravity about 2.65; ordinary heft for a common light-colored mineral. — https://lithomap.app/resources/mineral-identification/quartz
- Barite: Unusually heavy for a pale nonmetallic mineral; around 4.5. — https://lithomap.app/resources/mineral-identification/barite
- Galena: Very dense, commonly around 7.5, with lead-safe handling required. — https://lithomap.app/resources/mineral-identification/galena
- Gold: Exceptionally dense when pure, but host rock, pores, and other metals lower bulk measurements. — https://lithomap.app/resources/mineral-identification/gold

## Common mistakes

- Letting the specimen touch the cup
- Leaving bubbles on rough surfaces
- Using a scale too coarse for a small sample
- Ignoring absorbent thread or failing to tare the suspension
- Testing porous, mixed, or water-sensitive material as though it were a single mineral

## Safety and limitations

- Do not immerse unknown mine waste, lead-bearing dust, soluble salts, reactive material, radioactive candidates, or specimens that could contaminate the water.
- Treat the used water and container as contaminated when the specimen has any hazard uncertainty; do not use food vessels.
- Wash hands and work surfaces after handling dense ore minerals.
- Density supports identification but does not determine purity, metal content, value, or safe handling.

## Frequently asked questions

### Is heft enough to identify a mineral?

No. Heft can flag an unusually light or heavy specimen, but size and shape bias perception. A measurement plus independent properties is much stronger.

### Why does a porous rock give a poor result?

Open pores trap air and then absorb water, so the displaced volume and submerged reading change during the test.

### Are density and specific gravity identical?

Density has units of mass per volume. Specific gravity is a dimensionless ratio to water. Their numerical values can look similar in common metric units, but they are different quantities.

## Authoritative sources

- Minerals and their physical properties — U.S. National Park Service: https://www.nps.gov/subjects/geology/minerals.htm
- Natural Gemstones: Mineral Gemstones — U.S. Geological Survey: https://pubs.usgs.gov/gip/gemstones/mineral.html
- Kansas Rocks and Minerals: Mineral Identification — Kansas Geological Survey: https://www.kgs.ku.edu/Publications/Bulletins/ED2/07_ident.html

This method supports preliminary field identification. It is not laboratory confirmation, appraisal, hazard clearance, proof of origin, or permission to collect or alter a specimen.