Brewsterite-Sr is a member of the zeolite group often found as delicate, glassy, prismatic crystals in basaltic cavities. Collectors look for its distinctive pearly luster on cleavage planes and its typical occurrence in association with other zeolites like heulandite.

Hardness

5-5.5

Mohs

Luster

Vitreous to pearly on {010}

Streak

White

Transparency

Transparent

mineraluncommonZeolite Group family

Brewsterite-Sr

Hardness: 5-5.5
Luster: Vitreous to pearly on {010}
Streak: White
Transparency: Transparent

Is this brewsterite-sr?

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 brewsterite-sr with a known reference. Brewsterite-Sr sits at Mohs 5-5.5, 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 pearly on {010}.
4
Match the color range
Compare against the expected color range: white, yellowish white, gray.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: prismatic.

Often confused with

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

mineral

Heulandite

Mohs 3.5-4

How to tell apart: Brewsterite-Sr is noticeably harder (Mohs 5-5.5 vs. 3.5-4).

How to tell apart: Brewsterite-Sr is noticeably harder (Mohs 5-5.5 vs. 3.5-4).

How to tell apart: Brewsterite-Sr is noticeably harder (Mohs 5-5.5 vs. 4).

Compare →

Often found alongside brewsterite-sr

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

All properties

Chemical formula: Sr(Al₂Si₆)O₁₆·5H₂O
Mohs hardness: 5-5.5
Density: 2.45 g/cm³
Colors: White Yellowish white Gray
Streak: White
Luster: Vitreous to pearly on {010}
Transparency: Transparent
Crystal system: Monoclinic
Crystal habit: Prismatic
Cleavage: {010}, perfect
Rarity: Uncommon
Uses: Collector
Host rock: Hydrothermally deposited in druses lining cavities in basalts and schists; more rarely in ore deposits

Where rockhounds find brewsterite-sr

Classic worldwide localities

Strontian, Argyllshire, Scotland
Burpala massif, about 120 km north of Lake Baikal, eastern Siberia, Russia
Yellow Lake, near Olalla, British Columbia, Canada

Field-hunting tip

Where it forms: Hydrothermally deposited in druses lining cavities in basalts and schists; more rarely in ore deposits. If you start seeing zeolites, calcite, quartz in float, you are in the right ground. Typical habit: prismatic. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify brewsterite-sr?+

Mohs hardness is 5-5.5. Luster: vitreous to pearly on {010}. The streak is white. Common colors include white, yellowish white, gray.

Where is brewsterite-sr found?+

Notable localities include Strontian, Argyllshire, Scotland; Burpala massif, about 120 km north of Lake Baikal, eastern Siberia, Russia; Yellow Lake, near Olalla, British Columbia, Canada.

What rocks look like brewsterite-sr?+

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

What minerals are found with brewsterite-sr?+

Brewsterite-Sr commonly co-occurs with Zeolites, Calcite, Quartz. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does brewsterite-sr form in?+

Where it forms: Hydrothermally deposited in druses lining cavities in basalts and schists; more rarely in ore deposits. Working float back to the host body is the standard way to chase a fresh occurrence.

What is brewsterite-sr used for?+

Brewsterite-Sr is used in collector.

Find brewsterite-sr on the map

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