Geosmin

What Geosmin smells like

Geosmin has a distinct earthy or musty odour, with a human detection threshold around 0.006-0.01 micrograms per litre of water, and it is responsible for the earthy taste of beetroot. A perfumery retailer notes that it is used only very dilute and reads as harsh at full strength. PubChem links the compound to natural-product occurrence data (LOTUS).

Leading note

Earthy

Clear facets

Musty

Supporting facets

Beetroot, damp

Character

Potent, damp

• earthy
• musty
• beetroot
• damp soil

What makes Geosmin distinctive

The smell of wet soil itself, detectable at parts per trillion.

How Geosmin is used

Used in rain, petrichor and earth accords, always at very high dilution; at full strength it reads as harsh.

Typical role: modifier (used in small amounts to change the character of a blend).

How Geosmin differs from similar materials

Terrasol

Terrasol is earth after rain, camphoraceous and rooty; geosmin is wet soil itself, with a beetroot edge.

Each difference compares the published descriptions of the two materials. Smell varies with grade, supplier and dilution; compare them side by side on blotters before substituting one for another.

Formulation considerations

This CAS is the racemate as PubChem records it; natural geosmin is the (-)-enantiomer (CAS 19700-21-1). The formulas use it at 0.1-1%.

Identity and classification

Type

Aroma chemical

Origin

Occurs in nature

Odour family

Green / Woody

Note position

Heart to base note

Physical form at room temperature

Liquid. A colourless oil (Sigma-Aldrich), usually supplied for perfumery already diluted, for example to 1% in DPG.

Also known as

(±)-Geosmin, Octahydro-4,8a-dimethyl-4a(2H)-naphthalenol

CAS number

23333-91-7

Molecular formula

C12H22O

Molecular weight

182.3 g/mol

IUPAC name

4,8a-dimethyl-1,2,3,4,5,6,7,8-octahydronaphthalen-4a-ol

The CAS number, formula and molecular weight are taken from PubChem compound 1213, whose own record lists this CAS number; checked 24 October 2026.

Safety and compliance

Hazard classification of the neat substance, as PubChem summarises it, read 26 October 2026. Companies notifying the ECHA C&L Inventory report it as not meeting the GHS hazard criteria (99 of 99 reports). Unless it is harmonised, this is the notifiers' own classification, not a binding one.

This page is general information, not a safety assessment or a specification. Confirm identity, composition, IFRA status and allergen content from your supplier's documents for the lot you hold.

Materials it works with

• Patchouli Oil

  Essential oil · Woody / Chypre — earthy, woody, camphoraceous, dark

• Vetiver Oil

  Essential oil · Woody / Green — earthy, smoky, woody, rooty

• 1-Octen-3-ol

  Aroma chemical · Green / Aromatic — mushroom, earthy, green, herbal

Geosmin is also suggested as a partner on the pages for Terrasol.

Used in formulas and accords

Used in 16 published formulas

Geosmin is an ingredient in 11 perfume formulas and 5 accords in the Formula & Accord Library.

Community formulas

• Gun Powder Accord

  Community Formula · Accord · listed as “Geosmin 1% (23333-91-7)”, at 1%

• Hazelnut Accord

  Community Formula · Accord · listed as “Geosmin 1%”, at 1%

• Rain Accord

  Community Formula · Accord · listed as “Geosmin (23333-91-7) 0.1%”, at 0.1%

RUŌOD House Originals

Original compositions by RUŌOD House.

• Asphalt Peony

  RUŌOD House Creation · listed as “Geosmin 0.1% DPG”, at 0.1% in DPG

• Bright Wolf

  RUŌOD House Creation · listed as “Geosmin 0.1% DPG”, at 0.1% in DPG

• Guava Monsoon

  RUŌOD House Original · listed as “Geosmin 0.1% DPG”, at 0.1% in DPG

• Iris Weather

  RUŌOD House Original · listed as “Geosmin 0.1% DPG”, at 0.1% in DPG

• Iron Rain

  RUŌOD House Creation · listed as “Geosmin 0.1% DPG”, at 0.1% in DPG

• Ivy Wall

  RUŌOD House Original · listed as “Geosmin 0.1% DPG”, at 0.1% in DPG

• Moss Cathedral

  RUŌOD House Original · listed as “Geosmin 0.1% DPG”, at 0.1% in DPG

• Petrichor Stone Accord

  RUŌOD House Accord · listed as “Geosmin 0.1% DPG”, at 0.1% in DPG

• Rain on Linen

  RUŌOD House Original · listed as “Geosmin 0.1% DPG”, at 0.1% in DPG

• Rhubarb Quarry

  RUŌOD House Original · listed as “Geosmin 0.1% DPG”, at 0.1% in DPG

• Root Rain

  RUŌOD House Original · listed as “Geosmin 0.1% DPG”, at 0.1% in DPG

• Wet Bark Accord

  RUŌOD House Accord · listed as “Geosmin 0.1% DPG”, at 0.1% in DPG

• Ylang Rain Shelter

  RUŌOD House Original · listed as “Geosmin 0.1% DPG”, at 0.1% in DPG

Further reading

• Green Notes in Perfumery: Leaf, Galbanum and Violet Leaf

  The green palette — cis-3-hexenol, galbanum, violet leaf, styrallyl acetate — what green notes do, dosage, restrictions and pairings.

Questions about Geosmin

Sources

• PubChem — compound 1213, checked 24 October 2026.
• PubChem — GHS classification (the ECHA C&L Inventory notifications and any harmonised EU entry), read 26 October 2026.
• Wikipedia — Geosmin — published perfumery reference.
• Premiere Peau — Geosmin — published perfumery reference.
• PubChem — Octahydro-4,8a-dimethyl-4a(2H)-naphthol (CID 1213) — odour database.
• Olfactory profile: the RUŌOD Lab team's synthesis of the published descriptions above, reviewed 26 October 2026. Evidence: more than one published description. Classification and the short description: revision 1. Descriptions of odour are judgement, not measurement.