Frankhawthorneite is a rare copper tellurate mineral typically found as small, dark green to black tabular crystals. It is primarily known from the Centennial Eureka mine in Utah, where it occurs as a secondary mineral in oxidized tellurium-rich ore zones.

Hardness

3-4

Mohs

Luster

Vitreous

Streak

Pale leaf-green

Transparency

Transparent

mineralrare

Frankhawthorneite

Hardness: 3-4
Luster: Vitreous
Streak: Pale leaf-green
Transparency: Transparent

No image

Is this frankhawthorneite?

5-step field check

Run through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.

1
Test the hardness
Try to scratch frankhawthorneite with a known reference. Frankhawthorneite sits at Mohs 3-4, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Streak: pale leaf-green.
3
Read the luster
Hold the specimen under a strong light. Luster: vitreous.
4
Match the color range
Compare against the expected color range: medium leaf green.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: bladed, prismatic.

Often confused with

Frankhawthorneite vs. its common look-alikes, and how to tell them apart in the field.

mineral

Quetzalcoatlite

Mohs 3

How to tell apart: Luster reads vitreous on Frankhawthorneite and pearly to dull on Quetzalcoatlite.

Often found alongside frankhawthorneite

Minerals reported to co-occur with frankhawthorneite. Spotting these in float or country rock is a strong cue you are in the right ground.

All properties

Chemical formula: Cu₂TeO₄(OH)₂
Mohs hardness: 3-4
Density: 5.44 g/cm³
Colors: Medium leaf green
Streak: Pale leaf-green
Luster: Vitreous
Transparency: Transparent
Crystal system: Monoclinic
Crystal habit: Bladed, prismatic
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: A very rare secondary mineral formed by the oxidization of primary Cu–Te-bearing sulfides

Where rockhounds find frankhawthorneite

Classic worldwide localities

The Centennial Eureka mine, Juab County, Utah, USA (type locality)

Field-hunting tip

Where it forms: A very rare secondary mineral formed by the oxidization of primary Cu–Te-bearing sulfides. If you start seeing mcalpineite, hematite, acanthite in float, you are in the right ground. Typical habit: bladed, prismatic. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify frankhawthorneite?+

Mohs hardness is 3-4. Luster: vitreous. The streak is pale leaf-green. Common colors include medium leaf green.

Where is frankhawthorneite found?+

Notable localities include The Centennial Eureka mine, Juab County, Utah, USA (type locality).

Is frankhawthorneite safe to handle?+

Frankhawthorneite contains copper. Contains copper and tellurium; wash hands thoroughly after handling and avoid ingestion or inhalation of dust.

What rocks look like frankhawthorneite?+

Frankhawthorneite is most often confused with Quetzalcoatlite, Tlapallite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with frankhawthorneite?+

Frankhawthorneite commonly co-occurs with Mcalpineite, Hematite, Acanthite, Chrysocolla, Connellite, Enargite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does frankhawthorneite form in?+

Where it forms: A very rare secondary mineral formed by the oxidization of primary Cu–Te-bearing sulfides. Working float back to the host body is the standard way to chase a fresh occurrence.

What is frankhawthorneite used for?+

Frankhawthorneite is used in collector.

Find frankhawthorneite on the map

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