Diaoyudaoite is a rare sodium aluminate mineral discovered in heavy mineral sands. It typically occurs as small, colorless tabular crystals and is noted for its unique composition relative to more common aluminum-bearing minerals.

Hardness

7.6

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrare

Diaoyudaoite

Hardness: 7.6
Luster: Vitreous
Streak: White
Transparency: Transparent

Is this diaoyudaoite?

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 diaoyudaoite with a known reference. Diaoyudaoite sits at Mohs 7.6, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Streak: white.
3
Read the luster
Hold the specimen under a strong light. Luster: vitreous.
4
Match the color range
Compare against the expected color range: colorless, light green.
5
Look at form & habit
Crystal system: hexagonal. Typical habit: tabular crystals.

Often confused with

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

mineral

Corundum

Mohs 9

How to tell apart: Corundum is the harder of the two (Mohs 9 vs. 7.6); luster reads vitreous on Diaoyudaoite and adamantine to vitreous; pearly on partings on Corundum.

Often found alongside diaoyudaoite

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

All properties

Chemical formula: NaAl₁₁O₁₇
Mohs hardness: 7.6
Density: 3.30 g/cm³
Colors: Colorless Light green
Streak: White
Luster: Vitreous
Transparency: Transparent
Crystal system: Hexagonal
Crystal habit: Tabular crystals
Cleavage: One direction, good
Rarity: Rare
Uses: Collector
Host rock: In the heavy-mineral (S.G. > 2.8) fraction of the surface layer of sea-floor muds at about 1500 m water depth

Where rockhounds find diaoyudaoite

Classic worldwide localities

Okinawa Trough, near Diaoyudao Island, a few km northeast of Taiwan

Field-hunting tip

Where it forms: In the heavy-mineral (S.G. > 2.8) fraction of the surface layer of sea-floor muds at about 1500 m water depth. If you start seeing chromium inclusions, epidote, dolomite in float, you are in the right ground. Typical habit: tabular crystals. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify diaoyudaoite?+

Mohs hardness is 7.6. Luster: vitreous. The streak is white. Common colors include colorless, light green.

Where is diaoyudaoite found?+

Notable localities include Okinawa Trough, near Diaoyudao Island, a few km northeast of Taiwan.

What rocks look like diaoyudaoite?+

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

What minerals are found with diaoyudaoite?+

Diaoyudaoite commonly co-occurs with Chromium inclusions, Epidote, Dolomite, Muscovite, Chlorite, Biotite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does diaoyudaoite form in?+

Where it forms: In the heavy-mineral (S.G. > 2.8) fraction of the surface layer of sea-floor muds at about 1500 m water depth. Working float back to the host body is the standard way to chase a fresh occurrence.

What is diaoyudaoite used for?+

Diaoyudaoite is used in collector.

Find diaoyudaoite on the map

RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.