Bigcreekite is an extremely rare barium-calcium silicate mineral known almost exclusively from its type locality at the Big Creek drainage in California. It typically occurs as small, colorless, platy, or tabular crystals associated with other rare barium minerals in metamorphic rock environments.

Hardness

2-3

Mohs

Luster

Vitreous to pearly

Streak

White

Transparency

Translucent

mineralrare

Bigcreekite

Hardness: 2-3
Luster: Vitreous to pearly
Streak: White
Transparency: Translucent

Is this bigcreekite?

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 bigcreekite with a known reference. Bigcreekite sits at Mohs 2-3, 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.
4
Match the color range
Compare against the expected color range: colorless, white.
5
Look at form & habit
Crystal system: orthorhombic. Typical habit: subhedral crystals, tabular.

Often confused with

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

How to tell apart: Streak differs, so Bigcreekite leaves white, Delrioite leaves pale yellow green.

How to tell apart: Apophyllite is the harder of the two (Mohs 4-5 vs. 2-3).

Compare →

Often found alongside bigcreekite

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

All properties

Chemical formula: BaSi₂O₅·4H₂O
Mohs hardness: 2-3
Density: 2.66 g/cm³
Colors: Colorless White
Streak: White
Luster: Vitreous to pearly
Transparency: Translucent
Crystal system: Orthorhombic
Crystal habit: Subhedral crystals, tabular
Cleavage: Perfect on {001} and {010}
Rarity: Rare
Uses: Collector
Host rock: Filling fractures in gneiss near the margins of a granodiorite pluton

Where rockhounds find bigcreekite

Classic worldwide localities

Esquire #7 claim, west side of Big Creek, eastern Fresno County, and on the northwestern slope of Trumbull Peak, Mariposa County, California, USA

Field-hunting tip

Where it forms: Filling fractures in gneiss near the margins of a granodiorite pluton. If you start seeing sanbornite, quartz, diopside in float, you are in the right ground. Typical habit: subhedral crystals, tabular. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify bigcreekite?+

Mohs hardness is 2-3. Luster: vitreous to pearly. The streak is white. Common colors include colorless, white.

Where is bigcreekite found?+

Notable localities include Esquire #7 claim, west side of Big Creek, eastern Fresno County, and on the northwestern slope of Trumbull Peak, Mariposa County, California, USA.

What rocks look like bigcreekite?+

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

What minerals are found with bigcreekite?+

Bigcreekite commonly co-occurs with Sanbornite, Quartz, Diopside, Pyrrhotite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does bigcreekite form in?+

Where it forms: Filling fractures in gneiss near the margins of a granodiorite pluton. Working float back to the host body is the standard way to chase a fresh occurrence.

What is bigcreekite used for?+

Bigcreekite is used in collector.

Find bigcreekite on the map

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