Hogarthite is a rare sodium potassium calcium silicate, typically tan to white to colorless. It was approved as a distinct mineral species in 2009. It was first described from the Poudrette quarry (level 4), Montérégie, Quebec, Canada.

Hardness

Mohs

Luster

Satiny to silky to sub-vitreous

Streak

White

Transparency

Transparent to translucent

mineralrare

Hogarthite

Hardness: ~4
Luster: Satiny to silky to sub-vitreous
Streak: White
Transparency: Transparent to translucent

No image

Is this hogarthite?

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 hogarthite with a known reference. Hogarthite sits at Mohs ~4, 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: satiny to silky to sub-vitreous.
4
Match the color range
Compare against the expected color range: tan, white, colorless zoned.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: tabular crystals.

Often confused with

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

mineral

Sapphirine

Mohs 7.5

How to tell apart: Sapphirine is the harder of the two (Mohs 7.5 vs. ~4); luster reads satiny to silky to sub-vitreous on Hogarthite and vitreous on Sapphirine.

Compare →

Often found alongside hogarthite

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

All properties

Chemical formula: (Na,K)₂CaTi₂Si₁₀O₂₆·8H₂O
Mohs hardness: ~4
Density: 2.40 g/cm³
Colors: Tan WhiteColorless zoned
Streak: White
Luster: Satiny to silky to sub-vitreous
Transparency: Transparent to translucent
Crystal system: Monoclinic
Crystal habit: Tabular crystals
Cleavage: Perfect on {010}
Rarity: Rare
Uses: Collector
Host rock: In metasomatically altered marble xenoliths in a breccia zone associated with an alkaline intrusive complex

Where rockhounds find hogarthite

Classic worldwide localities

Poudrette quarry (level 4), Mont Saint-Hilaire, La-Vallée-du-Richelieu RCM, Montérégie, Quebec, Canada

Field-hunting tip

Where it forms: In metasomatically altered marble xenoliths in a breccia zone associated with an alkaline intrusive complex. If you start seeing calcite, quartz, haineaultite 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 hogarthite?+

Mohs hardness is ~4. Luster: satiny to silky to sub-vitreous. The streak is white. Common colors include tan, white, colorless zoned.

Where is hogarthite found?+

Notable localities include Poudrette quarry (level 4), Mont Saint-Hilaire, La-Vallée-du-Richelieu RCM, Montérégie, Quebec, Canada.

What rocks look like hogarthite?+

Hogarthite is most often confused with Sapphirine. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with hogarthite?+

Hogarthite commonly co-occurs with Calcite, Quartz, Haineaultite, Labuntsovite-Mn, Lemoynite, Chabazite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does hogarthite form in?+

Where it forms: In metasomatically altered marble xenoliths in a breccia zone associated with an alkaline intrusive complex. Working float back to the host body is the standard way to chase a fresh occurrence.

What is hogarthite used for?+

Hogarthite is used in collector.

Find hogarthite on the map

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