Warwickite is a rare borate mineral that typically forms elongated or prismatic dark-colored crystals in metamorphosed limestones. It is most famous for its occurrence in the contact metamorphic zones of the New York Highlands, where it appears alongside various magnesium-rich silicates.

Hardness

3-4

Mohs

Luster

Submetallic

Streak

Black

Transparency

Opaque

mineralrare

Warwickite

Hardness: 3-4
Luster: Submetallic
Streak: Black
Transparency: Opaque

Is this warwickite?

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 warwickite with a known reference. Warwickite 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. Warwickite leaves a black streak.
3
Read the luster
Hold the specimen under a strong light. Warwickite typically shows a submetallic luster.
4
Match the color range
Compare against the expected color range: black, dark brown, reddish-brown.
5
Look at form & habit
Crystal system: orthorhombic. Typical habit: prismatic crystals, elongated, acicular.

Often confused with

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

mineral

Ludwigite

Mohs 5

How to tell apart: Ludwigite is the harder of the two (Mohs 5 vs. 3-4).

How to tell apart: Streak differs — Warwickite leaves black, Szaibelyite leaves white; luster reads submetallic on Warwickite and dull on Szaibelyite.

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Often found alongside warwickite

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

All properties

Chemical formula: (Mg,Ti,Fe³⁺,Al)₂(O,OH)BO₃
Mohs hardness: 3-4
Density: 3.36-3.41 g/cm³
Colors: Black Dark Brown Reddish-brown
Streak: Black
Luster: Submetallic
Transparency: Opaque
Crystal system: Orthorhombic
Crystal habit: Prismatic Crystals, Elongated, Acicular
Cleavage: Perfect in One Direction
Rarity: Rare
Uses: Collector
Host rock: Metamorphosed Limestone, Skarn Deposits
Typical price: $20-150 per specimen

Where rockhounds find warwickite

Classic worldwide localities

Warwick, New York, USA
Amity, New York, USA
Glenelg, Scotland
Ladoga Lake, Russia

Field-hunting tip

Look in metamorphosed limestone, skarn deposits country — that is the host setting where warwickite typically forms. If you start seeing spinel, calcite, serpentine in float, you are in the right ground. Field specimens usually show a prismatic crystals, elongated, acicular habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify warwickite?+

Mohs hardness is 3-4. It typically shows a submetallic luster. The streak is black. Common colors include black, dark brown, reddish-brown.

Where is warwickite found?+

Notable localities include Warwick, New York, USA; Amity, New York, USA; Glenelg, Scotland; Ladoga Lake, Russia.

How much is warwickite worth?+

Typical asking prices fall in the range of $20-150 per specimen. Quality, size, and provenance can move individual specimens well outside that range.

What rocks look like warwickite?+

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

What minerals are found with warwickite?+

Warwickite commonly co-occurs with Spinel, Calcite, Serpentine, Chondrodite, Phlogopite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does warwickite form in?+

Warwickite typically forms in metamorphosed limestone, skarn deposits. Working float back to the host body is the standard way to chase a fresh occurrence.

What is warwickite used for?+

Warwickite is used in collector.

Find warwickite on the map

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