Symbol: Tm
Atomic Number: 69
Atomic Mass: 168.93 u
Classification: Lanthanides (Rare Earth Elements)
Group: f-block, Period 6
Physical State: Solid metal at room temperature
Density: 9.32 g/cm³
Melting Point: 1,545°C (2,813°F)
Boiling Point: 1,950°C (3,542°F)
Color: Bright silvery-gray metallic luster
Crystal Structure: Hexagonal close-packed
Magnetic Properties: Paramagnetic
Thulium is the rarest of all the naturally occurring lanthanides, making it one of the least abundant elements on Earth. Despite its scarcity, it has unique properties that make it valuable in specialized applications, particularly in portable X-ray devices and high-temperature superconductors. Its distinctive bright silvery appearance and exceptional resistance to corrosion in dry air make it a remarkable element in the rare earth family.
Discovery Date: 1879
Discoverer: Per Teodor Cleve (Swedish chemist)
Location: Uppsala University, Sweden
Method: Spectroscopic analysis of erbia
First Isolation: 1911 by Charles James
Name Origin: Named after "Thule"
Thule Reference: Ancient name for Scandinavia
Historical Context: Ultima Thule (most distant place)
Symbolic Meaning: Represents the far north
Cultural Significance: Norse mythology connection
Per Teodor Cleve's discovery of thulium in 1879 was a masterpiece of 19th-century analytical chemistry. While examining erbia (erbium oxide) samples, Cleve noticed unusual spectral lines that didn't match any known element. His meticulous work revealed not just thulium, but also holmium in the same year. The element's name, derived from Thule (the ancient name for Scandinavia), reflects Cleve's Swedish heritage and the mythical "far northern land" of classical geography. It took another 32 years before Charles James successfully isolated pure thulium metal in 1911, highlighting just how challenging it was to work with rare earth elements using early 20th-century techniques.
| Location/Source | Abundance | Typical Concentration | Notes |
|---|---|---|---|
| Earth's Crust | 0.52 ppm | Extremely rare | Rarest naturally occurring lanthanide |
| Seawater | ~0.00002 ppm | Trace amounts | Virtually undetectable levels |
| Monazite Sand | 0.007% | Primary commercial source | Main rare earth mineral |
| Bastnäsite | 0.01% | Secondary source | Carbonate-fluoride mineral |
| Xenotime | 0.03% | Rare phosphate mineral | Higher thulium concentration |
Monazite: (Ce,La,Th,Nd,Y)PO₄ - Most common source
Bastnäsite: (Ce,La)CO₃F - Secondary commercial source
Xenotime: YPO₄ - Richest in heavy rare earths
Gadolinite: Y₂FeBe₂Si₂O₁₀ - Historical source
Euxenite: (Y,Ca,Ce,U,Th)(Nb,Ta,Ti)₂O₆
Essential Function: No known biological role
Toxicity: Generally considered non-toxic
Bioaccumulation: Does not bioaccumulate
Plant Uptake: Minimal absorption by plants
Environmental Impact: Very low due to scarcity
Thulium's environmental distribution is remarkably limited due to its status as the rarest naturally occurring lanthanide. It appears primarily in rare earth mineral deposits, with concentrations so low that dedicated thulium mining is economically unfeasible. The element is typically recovered as a byproduct of other rare earth extraction processes. Its environmental impact is minimal due to its scarcity and relatively benign chemical behavior. Unlike some rare earth elements, thulium doesn't concentrate significantly in any particular environmental compartment, remaining dispersed at extremely low levels throughout the Earth's crust.
Portable X-ray Units: Thulium-170 in medical imaging
Cancer Treatment: Radioisotope therapy research
Dental X-rays: Some portable dental equipment
Emergency Medicine: Field X-ray devices
Research: Medical isotope studies
High-end Jewelry: Extremely rare decorative metal
Collector Items: Element collection samples
Scientific Instruments: Specialized detectors
Research Equipment: Laboratory standards
Educational Materials: Chemistry demonstrations
Quantum Research: Quantum computing studies
Materials Science: Advanced alloy research
Superconductor Research: High-temperature studies
Optical Research: Laser development
Nuclear Research: Isotope production
Quantum Dots: Advanced semiconductor research
Catalysis: Specialized chemical processes
Magnetism Studies: Magnetic property research
Energy Research: Advanced battery studies
Nanotechnology: Nanoparticle research
While thulium's extreme rarity limits its widespread use in daily life, its applications are highly specialized and critically important. The most notable everyday encounter with thulium occurs in portable X-ray equipment used in hospitals, dental offices, and emergency medical situations. Thulium-170, despite its short half-life, provides an excellent gamma-ray source for medical imaging. For the general public, thulium is more likely to be encountered in educational settings, element collections, or high-end scientific demonstrations rather than common household items.
High-Temperature Superconductors: Advanced conductor research
Specialized Magnets: High-performance magnetic applications
Quantum Electronics: Quantum device development
Laser Technology: Specialized laser systems
Semiconductor Research: Advanced electronic materials
Materials Testing: Advanced characterization
Catalytic Research: Specialized chemical processes
Alloy Development: High-performance materials
Nuclear Applications: Isotope production facilities
Standards & Calibration: Reference materials
Specialized Alloys: Ultra-high performance applications
Corrosion Resistance: Extreme environment materials
High-Temperature Applications: Aerospace components
Precision Instruments: Measurement devices
Research Facilities: Laboratory equipment
Catalysis Research: Novel catalyst development
Process Development: Specialized reactions
Analytical Chemistry: Standards and references
Material Synthesis: Advanced material production
Quality Control: Analytical applications
Despite its current limited industrial use due to extreme scarcity and high cost, thulium shows remarkable potential in cutting-edge technologies. Its unique magnetic and electronic properties make it a candidate for next-generation quantum computing devices, advanced superconductors, and specialized laser systems. As extraction and purification technologies improve, and as demand for ultra-high-performance materials grows in aerospace, defense, and advanced electronics, thulium may find expanded industrial applications. Current research focuses on understanding its fundamental properties to unlock future technological possibilities.
| Country/Region | Production Method | Annual Output | Market Share |
|---|---|---|---|
| China | Rare earth mining (byproduct) | ~50 kg/year | 85-90% |
| United States | Mountain Pass (California) | ~5 kg/year | 5-8% |
| Australia | Mount Weld project | ~3 kg/year | 3-5% |
| Brazil | Monazite sand processing | ~1-2 kg/year | 1-2% |
| Others | Various small operations | ~1 kg/year | <1% |
Ion Exchange: Primary separation technique
Solvent Extraction: Industrial purification
Fractional Crystallization: Laboratory-scale purification
Electrolysis: Metal production
Reduction: Calcium or lithium reduction
Price Range: $3,000-5,000 per gram
Market Size: Extremely limited (~$300,000 annually)
Supply Chain: Highly specialized
Investment: Research-driven demand
Future Outlook: Niche applications growth
Total Estimated Reserves: ~100,000 tons (theoretical)
China: 55% of known reserves
CIS Countries: 15% of reserves
United States: 13% of reserves
Other Countries: 17% of reserves
Recycling: Extremely limited due to scarcity
Substitution: Limited alternatives for specific uses
Conservation: Research-focused usage
Environmental Impact: Minimal due to low production
Supply Security: Dependent on rare earth industry
Thulium's supply chain is uniquely challenging due to its status as the rarest naturally occurring lanthanide. Unlike other rare earth elements, there are no dedicated thulium mines; all production comes as a byproduct of processing other rare earth ores. China's dominance in rare earth production translates to control over thulium supply, making it geopolitically sensitive despite minimal demand. The extremely limited annual production (estimated at less than 100 kg globally) means that any increase in demand could rapidly impact availability and pricing.
Medical Imaging: Portable X-ray devices
Research Standards: Scientific calibration
Quantum Research: Advanced physics studies
Superconductor Development: High-temperature research
Laser Technology: Specialized optical systems
High Unit Value: $3,000-5,000 per gram
Limited Market: Research and specialty applications
Strategic Importance: Critical for specific technologies
Investment Potential: Technology-driven growth
Supply Risk: Extremely limited availability
Fundamental Research: Understanding lanthanide chemistry
Quantum Mechanics: Advanced theoretical studies
Materials Science: Novel material development
Nuclear Physics: Isotope behavior studies
Crystallography: Structure determination
Quantum Computing: Potential quantum applications
Advanced Superconductors: Next-generation materials
Medical Isotopes: Enhanced radiotherapy
Nanotechnology: Specialized nanoparticles
Energy Storage: Advanced battery research
Thulium's strategic importance far exceeds what its limited availability might suggest. In the realm of advanced medical imaging, thulium-170 provides unique capabilities for portable X-ray devices that are crucial in emergency medicine and field applications. Its role in cutting-edge quantum research and superconductor development makes it invaluable for technological advancement. While substitutes exist for some applications, thulium's specific nuclear and electronic properties make it irreplaceable in certain high-tech applications. As technology advances toward quantum computing and advanced medical treatments, thulium's significance is likely to grow despite—or perhaps because of—its scarcity.
Rarest Lanthanide: Least abundant naturally occurring rare earth
Most Expensive Rare Earth: Costs more than gold
Shortest-Lived Medical Isotope: Tm-170 (128.6 days)
Highest Atomic Number: Among stable lanthanides
Most Challenging Isolation: Took 32 years to isolate pure metal
Magnetic Behavior: Shows unusual magnetic transitions
X-ray Properties: Excellent gamma-ray emission
Corrosion Resistance: Highly resistant in dry air
Color Changes: Compounds show varied colors
Crystal Structure: Perfect hexagonal symmetry
Norse Mythology: Named after legendary Thule
Antarctica Connection: Ultima Thule reference
Space Exploration: Potential spacecraft applications
Medical Breakthroughs: Revolutionary imaging capabilities
Quantum Physics: Fundamental particle studies
Element Collections: Holy grail for collectors
Science Fiction: Featured in advanced technology stories
Educational Value: Teaching tool for rarity concepts
Museum Displays: Rare science museum exhibits
Investment Interest: Speculative commodity trading
Here's something incredible: all the thulium ever produced by humanity would fit comfortably in a small refrigerator! With annual global production of less than 100 kilograms, thulium is literally rarer than many precious gems. If you could collect all the thulium in the Earth's crust, it would represent just 0.52 parts per million—meaning you'd need to process almost 2 million kilograms of average crustal rock to extract just one kilogram of thulium. Despite this extreme rarity, thulium-170 can penetrate human tissue with precisely the right energy for medical imaging, making it a perfect example of how nature provides exactly what we need in the most unexpected packages.
In 1879, Swedish chemist Per Teodor Cleve was working with erbia samples when he noticed mysterious spectral lines. His meticulous work revealed not one, but two new elements in the same year: thulium and holmium. Cleve's discovery methodology was so advanced for its time that it took other scientists decades to confirm his findings.
From discovery to isolation, thulium holds the record for the longest wait among lanthanides. Charles James finally isolated pure thulium metal in 1911, but only after developing revolutionary ion-exchange techniques. His success required processing tons of monazite sand for just a few grams of pure thulium.
The development of thulium-170 for portable X-ray devices represented a medical breakthrough. During the 1990s, the ability to bring X-ray capabilities to remote locations and emergency situations saved countless lives. Field medics and disaster response teams suddenly had diagnostic capabilities previously limited to hospitals.
When element collectors emerged in the late 20th century, thulium became the "holy grail" of element collecting. Pure thulium samples command prices rivaling fine jewelry, and authentic samples are so rare that many collections remain incomplete for decades waiting for a genuine thulium specimen.
The naming of thulium connects to one of history's most enduring mysteries. "Thule" represented the northernmost inhabited land known to ancient Greek and Roman geographers—possibly Iceland, the Faroe Islands, or northern Norway. When Cleve chose this name, he was connecting his discovery to the concept of "Ultima Thule," meaning "furthest Thule" or the edge of the known world. This poetic naming reflects how thulium represents the extremes of rarity and the boundaries of chemical discovery. Just as Thule was the mysterious far north to ancient explorers, thulium represents the frontier of rare earth chemistry to modern scientists.
| Property | Value | Units | Notes |
|---|---|---|---|
| Electron Configuration | [Xe] 4f¹³ 6s² | - | Thirteen 4f electrons |
| Oxidation States | +3 (most common), +2 | - | Tm³⁺ is most stable |
| Ionic Radius (Tm³⁺) | 0.869 | Å | Coordination number 6 |
| First Ionization Energy | 596.7 | kJ/mol | Relatively low |
| Electronegativity | 1.25 | Pauling scale | Typical lanthanide value |
Ground State: [Xe] 4f¹³ 6s²
Valence Electrons: 3 (6s² + one 4f)
Core Configuration: [Xe] 4f¹²
Magnetic Moment: 7.56 Bohr magnetons
Electronic Term: ²F₇/₂
Air Stability: Tarnishes slowly in moist air
Water Reaction: Reacts slowly with water
Acid Reaction: Dissolves in mineral acids
Halogen Reaction: Forms halides readily
Oxide Formation: Tm₂O₃ (sesquioxide)
Stable Isotope: ¹⁶⁹Tm (100% abundance)
Most Important Radioisotope: ¹⁷⁰Tm
¹⁷⁰Tm Half-life: 128.6 days
Decay Mode: Beta decay and electron capture
Medical Applications: Gamma ray source
Safety Classification: Generally safe
Storage: Inert atmosphere recommended
Handling: Standard metallic precautions
Disposal: Specialized rare earth recovery
Purity Requirements: 99.9%+ for research
Analyzing thulium requires sophisticated techniques due to its low concentrations and similarity to other lanthanides. Inductively Coupled Plasma Mass Spectrometry (ICP-MS) is the gold standard for thulium detection, capable of measuring concentrations down to parts per trillion. X-ray fluorescence spectroscopy provides rapid qualitative analysis, while neutron activation analysis offers exceptional sensitivity for trace amounts. The challenge in thulium analysis lies not just in detection, but in separation from other rare earth elements, requiring specialized ion-exchange chromatography or high-performance liquid chromatography (HPLC) with specific eluent systems.
Quantum Computing: Thulium-based qubits research
Superconductivity: High-temperature superconductor studies
Nanomedicine: Targeted drug delivery systems
Optical Computing: Quantum optical applications
Energy Storage: Advanced battery technologies
Quantum Sensors: Ultra-precise measurement devices
Medical Isotopes: Next-generation radiotherapy
Laser Applications: Ultra-high precision lasers
Magnetic Materials: Advanced magnetic systems
Catalysis: Novel catalytic processes
Recycling Technologies: Advanced recovery methods
Synthetic Alternatives: Artificial production research
Efficiency Improvements: Better extraction techniques
Conservation Strategies: Minimal waste processing
Circular Economy: Closed-loop applications
Medical Breakthroughs: Revolutionary diagnostic tools
Space Technology: Spacecraft applications
Defense Applications: Advanced military systems
Environmental Monitoring: Precision sensors
Fundamental Physics: New physics discoveries
The future of thulium lies at the intersection of extreme rarity and technological necessity. As quantum computing advances, thulium's unique magnetic properties may prove crucial for stable qubit systems. Medical applications are expanding beyond imaging to include targeted cancer therapy using thulium-based radiopharmaceuticals. Perhaps most intriguingly, advances in artificial element production might eventually allow synthetic thulium creation, potentially transforming it from the rarest lanthanide to a designed material with tailored properties. The next two decades may see thulium evolve from a laboratory curiosity to a cornerstone of quantum technology, representing humanity's ability to find profound uses for nature's scarcest materials.
Ground State: [Xe] 4f¹³ 6s² - The electron animation shows thulium's 69 electrons distributed across orbital shells, with particular attention to the thirteen 4f electrons that give thulium its unique magnetic properties. The visualization demonstrates how these electrons occupy specific orbital shapes and energy levels.
Conduction Behavior: As a typical lanthanide metal, thulium shows moderate electrical conductivity. The animation illustrates how valence electrons (primarily from the 6s orbital) contribute to metallic bonding and electrical conduction, while the 4f electrons remain largely localized and contribute to magnetic properties.
Temperature Effects: Increasing temperature causes greater electron thermal motion, which you can observe in the animation. Higher temperatures lead to increased electrical resistance as electron-phonon interactions become more prominent.
Applied Electric Field: When voltage is applied, you can observe electron drift in the conduction band, demonstrating how electric fields influence electron movement and create electrical current in the metal.
Electrical Resistivity (ρ): 676 nΩ·m (20°C)
Electrical Conductivity (σ): 1.48 × 10⁶ S/m
Temperature Coefficient: +3.9 × 10⁻³ K⁻¹
Hall Coefficient: -1.8 × 10⁻⁹ m³/C
Charge Carriers: Electrons (metallic conduction)
Carrier Concentration: ~10²³ electrons/cm³
Electron Mobility: ~10 cm²/(V·s)
Drift Velocity: v = μE (field-dependent)
Resistance vs Temperature: R(T) = R₀[1 + α(T-T₀)]
Debye Temperature: ~200 K
Melting Point Resistivity: ~1200 nΩ·m
Superconducting Transition: Not observed
Plasma Frequency: ~1.5 × 10¹⁶ Hz
Skin Depth (1 MHz): ~260 μm
AC Conductivity: σ(ω) = σ₀/(1 + jωτ)
Dielectric Constant: Metallic behavior
Ohm's Law Applications: Thulium follows Ohm's law (V = IR) in its metallic state, with linear current-voltage relationships under normal operating conditions. The high resistivity compared to common metals limits its use in power applications but makes it suitable for precision resistors.
Power Dissipation: P = I²R = V²/R = 1.48 × 10⁻⁶ W/A² per cubic meter. The relatively high resistance leads to significant Joule heating in current-carrying applications.
Thermal Considerations: The positive temperature coefficient means resistance increases with temperature, providing natural current limiting. For precision applications, temperature compensation is essential.
| Electrical Parameter | Value | Units | Engineering Significance |
|---|---|---|---|
| Resistivity (20°C) | 676 | nΩ·m | High resistance for lanthanide metal |
| Conductivity | 1.48 | MS/m | Moderate metallic conductivity |
| Hall Mobility | ~10 | cm²/(V·s) | Typical for lanthanide metals |
| Work Function | 3.2 | eV | Moderate electron emission barrier |
| Magnetic Susceptibility | +24,700 | ×10⁻⁶ (SI) | Strong paramagnetic behavior |
Precision Resistors: High stability reference elements
Magnetic Sensors: Paramagnetic detection systems
High-Temperature Electronics: Specialized applications
Research Instrumentation: Calibration standards
Current Density Limits: Thermal management required
Contact Resistance: Oxidation protection needed
Thermal Cycling: Expansion coefficient matching
Cost Factors: Extremely high material costs