There are parts of your history that still need shade. Proustite, ruby silver, darkens under light because even its beauty has limits of exposure. Privacy can be a form of preservation.
Intent
Energy & Passion
Transformation & ChangeClarity & FocusMotivation & Energy
Proustite belongs with nervous systems that are sensitive to exposure. Not fragile in the ordinary sense, but reactive to too much light, too much contact, too much...
Overview
The heart of the entry
Not every truth wants daylight immediately. Some parts of the past become damaged by too much exposure, not because...
Mineralogy
Trigonal
Proustite darkens in light. That is not metaphor, prolonged exposure decomposes the surface irreversibly, which is...
Formation
How it forms
Trigonal system — earth conditions, structure, and place.
Crystal system diagram represents the general trigonal classification. Diagram created by Crystalis for educational reference.
What your body knows
Energy & Passion
Proustite belongs with nervous systems that are sensitive to exposure. Not fragile in the ordinary sense, but reactive to too much light, too much contact, too much...
The Meaning
Proustite in the Crystalis dictionary
Not every truth wants daylight immediately. Some parts of the past become damaged by too much exposure, not because they are false, but because they are still too reactive to survive careless handling.
Proustite makes that condition exact. The ruby-red silver sulfosalt is famously photosensitive, darkening when exposed to too much light. The beauty remains real, but so does the need for shade.
Proustite is useful when the psyche is learning that privacy is not avoidance.
Some histories keep better when they are not overexposed.
Stone Lore
Stories carried through time
Cultural notes are presented as tradition and historical context — stories carried through time.
Unknown
Naming
Named in 1832 by Francois Sulpice Beudant in honor of Joseph Louis Proust (1754-1826), the French chemist who established the Law of Definite Proportions (Law of Constant Composition), one of the foundational principles of modern chemistry. Proust demonstrated that chemical compounds always contain elements in fixed proportions by mass, regardless of origin.
Origin lore
Mining History
Proustite was one of the most important silver ore minerals in historic silver mining districts: - The Erzgebirge (Saxony/Bohemia) silver mines that funded the Renaissance and gave us the word "dollar" (from "Joachimsthaler") produced...
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Historical note
Collector Significance
Proustite is one of the most prized mineral collector's species. Fine transparent red crystals with good crystal form are among the most valuable mineral specimens in the world. The photosensitivity adds urgency and difficulty to...
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Lore & history
"Ruby Silver"
The term "ruby silver" (Rotgiltigerz in German) was historically applied to both proustite and pyrargyrite, with proustite called "light red silver ore" (Lichtes Rotgiltigerz) and pyrargyrite called "dark red silver ore" (Dunkles...
Unknown
Earth Record
Mineralogy and formation
Proustite darkens in light. That is not metaphor, prolonged exposure decomposes the surface irreversibly, which is why collectors store ruby silvers in darkness and photographers avoid flash.
A silver arsenic sulfosalt (Ag₃AsS₃), one of the two ruby silvers, prized for deep scarlet-red translucency. Trigonal, prismatic to rhombohedral crystals with adamantine luster. Forms in low-temperature hydrothermal silver veins as a secondary mineral. Extremely soft (2–2.5 Mohs), specific gravity 5.57. Major historical sources include Chañarcillo, Chile (some of the finest 19th-century specimens), Freiberg in Saxony, and Cobalt, Ontario. Beautiful, photosensitive, and fragile.
Crystal system diagram represents the general trigonal classification. Diagram created by Crystalis for educational reference.
Trigonal structure
Chemical Formula
Ag3AsS3 (silver arsenic sulfide; a sulfoarsenide/sulfosalt)
Crystal System
Trigonal
Mohs Hardness
2
Specific Gravity
5.55-5.64
Luster
Adamantine to submetallic
Color
Red
IMA Status
species
Type Locality
Commonly cited as Jáchymov, Karlovy Vary Region, Czech Republic
IMA Number
pre-IMA (Grandfathered)
01
Mineral conditions gather
02
Structure begins to crystallize
03
Proustite records place and pressure
ChileGermanyCzech Republic
Telling it apart
Proustite is a silver arsenic sulfide that forms brilliant red translucent prismatic crystals, and the confusion involves pyrargyrite, cinnabar, and red glass. The species level separation from pyrargyrite is compositional: proustite is Ag3AsS3, the light ruby silver, while pyrargyrite is Ag3SbS3, the dark ruby silver. Visually, proustite tends toward a brighter, more scarlet red, while pyrargyrite is darker.
Hardness is about 2 to 2. 5, specific gravity 5. 57, and the crystal system is trigonal. Cinnabar is a mercury sulfide with different crystal habit and chemistry. Red glass lacks crystal structure and specific gravity. Proustite darkens on light exposure, so specimens should be stored in darkness. If the red silver mineral is bright red and forms prismatic trigonal crystals, proustite is likely, but distinguishing it from pyrargyrite usually requires analysis.
Spotting the real thing
Proustite: vivid red ("ruby silver"), specific gravity 5. 55-5. 64 (very heavy).
Adamantine luster. Mohs 2-2. 5 (soft).
PHOTOSENSITIVE: darkens permanently in light. If a claimed proustite does not darken after light exposure, it may be a different red mineral. Contains arsenic.
When energy feels stuck and the body won't respond. Proustite is placed on the body as an anchor point. Your shoulders drop. Your breath becomes shallow and barely audible. A heaviness settles in your limbs. This is dorsal vagal shutdown; your oldest survival circuit pulling you toward stillness, collapse, disconnection from sensation.
Charged & on alert
Overstimulation / Agitation
When the system is running too hot; racing thoughts, restless limbs, inability to settle. Your chest tightens. Your jaw clenches. Your breath moves higher, shallower, faster. This is sympathetic activation; your body mobilizing for fight or flight, muscles tensing, heart rate rising.
Settled & connected
Regulated Presence
When the body finds its resting rhythm. Proustite held or placed becomes a touchpoint for presence. Your chest opens. Your jaw unclenches. Your breath deepens into your belly. This is ventral vagal regulation; your body finding safety, social connection, steady presence.
These associations come from tradition and reflective practice — a way of working with the stone, not a medical prescription.
Somatic Practice
Simple ways to work with Proustite
◇
Hold
Carry Proustite in a pocket or place it over the heart center during a pause.
◌
Meditate
Let the stone become a quiet tactile anchor while the breath slows.
☽
Breathe
Breathe in softness. Breathe out tension. Keep the practice simple.
✎
Journal
Write with Proustite nearby to name the feeling without forcing a conclusion.
✋
Bodywork
Rest the stone near the chest, hand, or bedside as a reminder to soften.
⌂
Environment
Place it where you want a visual cue for care, repair, or steadiness.
Field Instruction
The Ruby Fire Witness
Honor the ruby fire you cannot touch.
3 min protocol
1
Place Proustite in a sealed glass display case or behind glass. Do NOT handle with bare hands — this mineral contains arsenic (silver arsenic sulfide). Sit 2-3 feet away. Settle your posture. Let your breath slow.
2
Observe the deep ruby-red translucent surface. Notice the adamantine luster, the way light seems to glow from within. Let your eyes soften. Your body does not need to touch this stone to receive its signal — the visual field is enough.
3
With each exhale, release one thing — a thought, a tension, a worry. The stone holds its own boundaries. You hold yours. Continue breathing. Notice where the body softens first.
4
After 3 minutes: check in. Has the breath changed? Has the jaw released? That shift — however small — is the protocol complete. The ruby fire witnessed. The body responded. No contact required.
Stone Intelligence
The fact that makes Proustite memorable
Proustite darkens in light. Not metaphor. Prolonged exposure decomposes the surface irreversibly.
A silver arsenic sulfide that teaches by disappearing when observed too long. The science documents photosensitive mineral decomposition. The practice is darkness.
This mineral requires you to protect it from the thing that reveals it.
SCI
Progress in the knowledge of ‘ruby silvers’: New structural and chemical data of pyrostilpnite, Ag3SbS3
Display only. Proustite contains arsenic and darkens permanently in light. There are parts of your history that still need shade.
The use case is understanding photosensitivity as a mineral principle: some things cannot survive being seen too long. Store in darkness. Observe briefly.
The practice is learning to protect what is vivid by limiting its exposure.
Sacred Match
Sacred Match prescribes Proustite when you report:
Too visible for too long
Skin tired of exposure
Keeping the brightest parts hidden
Speaking and then regretting the light
Needing privacy to stay intact
Tenderness that hardens under scrutiny
Sacred Match prescribes through physiological diagnosis, not preference. It queries the nervous system: current sensation, protective mechanism, and the biological need masked by both. When that triangulation reveals a system damaged by overexposure rather than by silence, proustite enters the protocol. It is prescribed as a lesson in measured contact and protected brilliance.
Visible -> too much gaze on the surface -> seeking shade
Hidden brightness -> value defended by withdrawal -> seeking protected expression
Regret after speaking -> exposure exceeded capacity -> seeking pacing
Tenderness hardened -> softness treated as risk -> seeking privacy
The prescription remains specific: Proustite is chosen when the body needs a visible object to organize sensation into sequence. The match is not aesthetic. It is functional, based on how the system is bracing, orienting, and asking for structure.
Pairings are treated like a recipe file: clear use, method, and safety.
Crystal Companion
Proustite + Amethyst
Use when
You want to layer the primary intention with another supportive tone.
How to work with it
Place the stones together during meditation, journaling, or a short reset.
Safety
Use as a reflective practice tool, not as a medical substitute.
Crystal Companion
Proustite + Rhodonite
Use when
You want to layer the primary intention with another supportive tone.
How to work with it
Place the stones together during meditation, journaling, or a short reset.
Safety
Use as a reflective practice tool, not as a medical substitute.
Crystal Companion
Proustite + Clear Quartz
Use when
You want to layer the primary intention with another supportive tone.
How to work with it
Place the stones together during meditation, journaling, or a short reset.
Safety
Use as a reflective practice tool, not as a medical substitute.
Crystal Companion
Proustite + Black Tourmaline
Use when
You want to layer the primary intention with another supportive tone.
How to work with it
Place the stones together during meditation, journaling, or a short reset.
Safety
Use as a reflective practice tool, not as a medical substitute.
Clear Quartz
The Careful Illumination.
Proustite is silver arsenic sulfide, trigonal at Mohs 2, a photosensitive mineral whose deep red darkens under light. Clear quartz helps frame the stone's rarity and fragility by providing clean optical contrast without demanding direct handling of the specimen. Place quartz behind the proustite specimen in low light, never under harsh direct sun.
Black Tourmaline
The Safety Perimeter.
Black tourmaline gives emotional and practical gravity to a mineral that is both delicate and arsenic-bearing. Tourmaline's boron-rich silicate body at Mohs 7 provides hard boundary energy beside proustite's soft, sensitive sulfosalt body. Keep proustite enclosed in a display box and set black tourmaline at the base of that box.
Rose Quartz
The Tenderness Around Severity.
Proustite can feel exacting, ruby-silver and dangerously beautiful. Rose quartz offsets that with softer pink silicon dioxide warmth, useful for collections built around shadowed reds and silver minerals. The pair allows the practitioner to hold both severity and gentleness in one display. Rose quartz on the same shelf but not touching, slightly to the left of the specimen.
Smoky Quartz
The Afterimage and Closure.
Smoky quartz helps the experience land after viewing a photosensitive, high-density mineral that carries more intensity than size suggests. Smoky quartz's irradiated silicon dioxide body provides grounding descent after the concentrated charge of a silver sulfosalt. Hold smoky quartz after handling storage materials, with proustite returned to darkness.
Pairing Caution
Proustite contains arsenic. Handle with care, store in darkness, and never use in elixirs.
Care & Cleansing
How to keep Proustite in good condition
Water Safe?
Keep dry
This stone should stay out of water. Water can dull the surface, destabilize the specimen, or damage the stone over time.
Sunlight Safe?
Use care
May fade or shift color in prolonged direct sun — keep exposure short and indirect.
Authenticity
What to check
Natural Proustite should usually feel cooler than plastic or resin on first touch and warm more slowly in the hand.
WARNING: Proustite contains arsenic (Ag3AsS3). Silver arsenic sulfide. Do NOT place in water or gem elixirs. Handle briefly, wash hands. Proustite is also photosensitive; it darkens permanently in light. Store in complete darkness in a sealed container. Recommended cleansing: visual observation only, in brief low light. Never display in bright light or sunlight.
Safety: Safe to own, display, and handle — wash your hands afterward. Do not make elixirs, place it in drinking water, or ingest it, and never inhale dust from raw or broken pieces.
Temperature
Natural Proustite should usually feel cooler than plastic or resin on first touch and warm more slowly in the hand.
Scratch logic
Use 2 on the Mohs scale as the check, not internet myths. A real specimen should behave in line with the hardness listed above.
Surface and luster
Look for a adamantine to submetallic surface quality rather than a painted or plastic shine.
Weight and density
The listed specific gravity is 5.55-5.64. If a specimen feels unusually light for its size, it may deserve a second look.
My Field Guide
Your private record and next steps
Journal
Add this stone to your private collection, then log what happened when you worked with it.
Shared Notes
Read public practice logs and pattern notes from the Crystalis community.
When members save a public field note for this stone, it will appear here.
Frequently Asked
Questions people ask about Proustite
What is Proustite?
Chemical formula: Ag3AsS3 (silver arsenic sulfide — a sulfoarsenide/sulfosalt). Mohs hardness: 2-2.5. Crystal system: Trigonal (space group R3c).
What is the Mohs hardness of Proustite?
Proustite has a Mohs hardness of 2-2.5.
Can Proustite go in water?
Safety Flags
What crystal system is Proustite?
Proustite crystallizes in the Trigonal (space group R3c).
What is the chemical formula of Proustite?
The chemical formula of Proustite is Ag3AsS3 (silver arsenic sulfide — a sulfoarsenide/sulfosalt).
How does Proustite form?
Formation Geology Proustite forms in the late, low-temperature stages of silver-bearing hydrothermal vein systems, typically epithermal to mesothermal environments: Epithermal silver deposits: Proustite crystallizes from relatively cool hydrothermal fluids (<250 degrees C) in the waning stages of silver vein mineralization. It is a classic "bonanza ore" mineral — found in pockets and vugs within silver veins where late-stage, As-enriched fluids deposited silver sulfosalts. The mineral assemblag
Sources & Citations
Where this entry can be checked
Back Matter
Readable for people. Structured for AI search.
Sources stay visible in the page so readers, search engines, and answer systems can follow the evidence trail.
01
SCI
Progress in the knowledge of ‘ruby silvers’: New structural and chemical data of pyrostilpnite, Ag3SbS3
Biagioni C., Zaccarini F., Roth P., Bindi L. (2020). Progress in the knowledge of ‘ruby silvers’: New structural and chemical data of pyrostilpnite, Ag3SbS3. Mineralogical Magazine. [SCI]DOI 10.1180/mgm.2020.37
02
SCI
Dervillite from Jáchymov, Czech Republic: a non-harmonic approach to the refinement of atomic displacement parameters of silver
Plášil J., Makovicky E., Petříček V., Škácha P. (2025). Dervillite from Jáchymov, Czech Republic: a non-harmonic approach to the refinement of atomic displacement parameters of silver. Mineralogical Magazine. [SCI]DOI 10.1180/mgm.2024.93
03
SCI
Study on the Cu–As–Sb–Ag–Bi–Pb–Te Sulfosalt Minerals from the Hydrothermal System of Southwestern Hokkaido, Japan
Yuningsih, Euis T., Matsueda, Hiroharu. (2018). Study on the Cu–As–Sb–Ag–Bi–Pb–Te Sulfosalt Minerals from the Hydrothermal System of Southwestern Hokkaido, Japan. Resource Geology. [SCI]DOI 10.1111/rge.12157
