Ferrierite-Mg is a rare zeolite mineral typically found in volcanic basalt cavities as delicate, pearly-white to colored sprays or radiating blades. Collectors primarily search for it in amygdules where it forms distinct, sharp, platy crystal clusters associated with other secondary minerals like calcite and analcime.

Hardness

3-3.5

Mohs

Luster

Vitreous to silky

Streak

White

Transparency

Transparent

mineralrareFerrierite family

Ferrierite-Mg

Hardness: 3-3.5
Luster: Vitreous to silky
Streak: White
Transparency: Transparent

Is this ferrierite-mg?

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 ferrierite-mg with a known reference. Ferrierite-Mg sits at Mohs 3-3.5, 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 to silky.
4
Match the color range
Compare against the expected color range: white, colorless, pink, orange, red.
5
Look at form & habit
Crystal system: orthorhombic. Typical habit: radial, tabular.

Often confused with

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

Often found alongside ferrierite-mg

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

All properties

Chemical formula: [Mg₂(K,Na)₂Ca₀.₅](Si₂₉Al₇)O₇₂·18H₂O
Mohs hardness: 3-3.5
Density: 2.06-2.23 g/cm³
Colors: White Colorless Pink Orange Red
Streak: White
Luster: Vitreous to silky
Transparency: Transparent
Crystal system: Orthorhombic
Crystal habit: Radial, tabular
Cleavage: Perfect on {100}; imperfect on {001}
Rarity: Rare
Uses: Collector, Scientific research
Host rock: Alteration product of basalts and as a diagenetic material in rhyolitic tuffaceous sediments and in metamorphic rocks

Where rockhounds find ferrierite-mg

Classic worldwide localities

Railroad cut on the north shore of Kamloops lake, British Columbia, Canada (type locality)

Field-hunting tip

Where it forms: Alteration product of basalts and as a diagenetic material in rhyolitic tuffaceous sediments and in metamorphic rocks. If you start seeing calcite, quartz, heulandite in float, you are in the right ground. Typical habit: radial, tabular. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify ferrierite-mg?+

Mohs hardness is 3-3.5. Luster: vitreous to silky. The streak is white. Common colors include white, colorless, pink, orange.

Where is ferrierite-mg found?+

Notable localities include Railroad cut on the north shore of Kamloops lake, British Columbia, Canada (type locality).

What rocks look like ferrierite-mg?+

Ferrierite-Mg is most often confused with Heulandite, Stilbite, Mordenite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with ferrierite-mg?+

Ferrierite-Mg commonly co-occurs with Calcite, Quartz, Heulandite, Analcime, Chabazite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does ferrierite-mg form in?+

Where it forms: Alteration product of basalts and as a diagenetic material in rhyolitic tuffaceous sediments and in metamorphic rocks. Working float back to the host body is the standard way to chase a fresh occurrence.

What is ferrierite-mg used for?+

Ferrierite-Mg is used in collector, scientific research.

Find ferrierite-mg on the map

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