# Hornblende vs. tourmaline: how to tell them apart

Canonical page: https://lithomap.app/resources/mineral-identification/compare/hornblende-vs-tourmaline
Last reviewed: September 17, 2026
Page purpose: Original LithoMap side-by-side field identification reference for search systems and language models.

## Summary

Hornblende and dark tourmaline can both form black elongate prisms. Hornblende has two good oblique cleavages and commonly splintery surfaces; tourmaline is harder, poorly cleaved, strongly striated, and commonly triangular in cross section.

## Bottom line

Check breakage and cross section. Repeated cleavage near 60 and 120 degrees favors hornblende; deep lengthwise grooves and a rounded-triangular section favor tourmaline.

## Side-by-side evidence

- Cleavage: Hornblende — Two good directions near 56 and 124 degrees Tourmaline — Poor to indistinct Interpretation — Cleavage geometry is the strongest distinction on broken grains.
- Habit and cross section: Hornblende — Elongate or splintery prisms, often diamond-shaped Tourmaline — Strongly striated trigonal prisms with triangular to rounded-triangular sections Interpretation — Natural crystal geometry can resolve intact specimens.
- Hardness: Hornblende — Mohs about 5 to 6 Tourmaline — Mohs about 7 to 7.5 Interpretation — Tourmaline commonly scratches quartz; hornblende generally does not.
- Typical setting: Hornblende — Igneous and metamorphic rocks such as diorite and amphibolite Tourmaline — Pegmatites, metamorphic rocks, veins, and granitic settings Interpretation — Context supports but cannot replace physical evidence.

## Field sequence

1. Inspect natural faces and cross section with a hand lens.
2. Look for deep lengthwise grooves on a triangular prism.
3. Use existing breaks to find repeated oblique cleavage.
4. Reserve hardness testing for expendable material.

## Limits and cautions

- Broken grains may lack recognizable crystal form.
- Dark color is shared and is not diagnostic.
- Do not scratch or break a potentially collectible tourmaline crystal.

## Frequently asked questions

### Is every black prismatic mineral tourmaline?

No. Hornblende, augite, staurolite, and other minerals can be dark and prismatic.

### Which mineral has cleavage?

Hornblende has two good oblique cleavage directions. Tourmaline has poor or indistinct cleavage.

### Can hornblende be triangular?

Its cross section can be angular or roughly six-sided, but the strongly striated rounded-triangular form is more characteristic of tourmaline.

## Related identification guides

- Hornblende: https://lithomap.app/resources/mineral-identification/hornblende
- Tourmaline: https://lithomap.app/resources/mineral-identification/tourmaline

## Authoritative sources

- Minerals and their physical properties — U.S. National Park Service: https://www.nps.gov/subjects/geology/minerals.htm
- Mohs Hardness Scale — U.S. National Park Service: https://www.nps.gov/articles/mohs-hardness-scale.htm
- Natural Gemstones: Mineral Gemstones — U.S. Geological Survey: https://pubs.usgs.gov/gip/gemstones/mineral.html

This reference supports preliminary field identification. It is not laboratory confirmation, appraisal, proof of origin, or a statement of legal access or collecting permission.