✦ MINERAL REFERENCE (50 ENTRIES)
Crystal Formula, Hardness & Care Table
Compare the formula, crystal system or structure, and Mohs hardness listed for all 50 entries in the encyclopedia. The care notes give a cautious starting point for handling a specimen; treatments, fractures and settings can change what an individual piece needs.
| Crystal / Mineral | Chemical Formula | Crystal System / Structure | Mohs Hardness | Care Notes |
|---|---|---|---|---|
| Amethyst | SiO₂ (Silicon Dioxide with Iron traces) | Trigonal (Hexagonal Prisms) | 7.0 | Start with a soft, dry cloth. Check treatments, cracks and settings before using water. Store separately and display away from strong sun and heat. |
| Rose Quartz | SiO₂ (Colored by microscopic dumortierite fibers) | Trigonal (Massive habits) | 7.0 | Start with a soft, dry cloth. Check treatments, cracks and settings before using water. Store separately and display away from strong sun and heat. |
| Clear Quartz | SiO₂ (Pure Crystalline Silica) | Trigonal (Six-sided prisms with pyramidal terminations) | 7.0 | Start with a soft, dry cloth. Check treatments, cracks and settings before using water. Store separately and display away from strong sun and heat. |
| Black Tourmaline | NaFe²⁺₃Al₆(BO₃)₃Si₆O₁₈(OH)₄ (Schorl) | Trigonal (Vertically striated prisms) | 7.0 – 7.5 | Start with a soft, dry cloth. Check treatments, cracks and settings before using water. Store separately and display away from strong sun and heat. |
| Citrine | SiO₂ (Ferric iron trace impurities) | Trigonal | 7.0 | Start with a soft, dry cloth. Check treatments, cracks and settings before using water. Store separately and display away from strong sun and heat. |
| Selenite | CaSO₄·2H₂O (Hydrated Calcium Sulfate) | Monoclinic | 2.0 (Very Soft — Scratches with fingernail) | Keep dry and remove loose dust gently with a soft brush. Avoid soaking. Store separately and display away from strong sun and heat. |
| Labradorite | (Ca,Na)(Al,Si)₄O₈ (Plagioclase Feldspar) | Triclinic | 6.0 – 6.5 | Start with a soft, dry cloth. Check treatments, cracks and settings before using water. Store separately and display away from strong sun and heat. |
| Lapis Lazuli | (Na,Ca)₈(AlSiO₄)₆(SO₄,S,Cl)₂ + FeS₂ | Aggregate (Isometric Lazurite + Pyrite) | 5.0 – 5.5 | Keep dry and remove loose dust gently with a soft brush. Avoid soaking. Store separately and display away from strong sun and heat. |
| Tiger's Eye | SiO₂ with iron oxide chatoyancy | Trigonal (Chatoyant fibrous quartz) | 6.5 – 7.0 | Start with a soft, dry cloth. Check treatments, cracks and settings before using water. Store separately and display away from strong sun and heat. |
| Carnelian | SiO₂ (Colored by iron oxide) | Trigonal (Microcrystalline Quartz) | 6.5 – 7.0 | Start with a soft, dry cloth. Check treatments, cracks and settings before using water. Store separately and display away from strong sun and heat. |
| Green Aventurine | SiO₂ + Cr-muscovite (Fuchsite) | Trigonal (Quartz with Fuchsite mica inclusions) | 6.5 – 7.0 | Start with a soft, dry cloth. Check treatments, cracks and settings before using water. Store separately and display away from strong sun and heat. |
| Black Obsidian | 70%+ SiO₂ (Rhyolitic Lava Glass) | Amorphous (Volcanic Silica Glass) | 5.0 – 5.5 | Start with a soft, dry cloth. Check treatments, cracks and settings before using water. Store separately and display away from strong sun and heat. |
| Rainbow Moonstone | (Na,K)AlSi₃O₈ (Orthoclase / White Labradorite) | Monoclinic / Triclinic | 6.0 – 6.5 | Keep dry and remove loose dust gently with a soft brush. Avoid soaking. Store separately and display away from strong sun and heat. |
| Malachite | Cu₂CO₃(OH)₂ (Copper Carbonate Hydroxide) | Monoclinic (Botryoidal & banded masses) | 3.5 – 4.0 (Soft — Handle with care) | Keep dry and remove loose dust gently with a soft brush. Avoid soaking. Store separately and display away from strong sun and heat. |
| Rainbow Fluorite | CaF₂ (Calcium Fluoride) | Isometric (Cubic & Octahedral crystals) | 4.0 | Keep dry and remove loose dust gently with a soft brush. Avoid soaking. Store separately and display away from strong sun and heat. |
| Pyrite | FeS₂ (Iron Disulfide) | Isometric (Natural Cubic & Pyritohedral crystals) | 6.0 – 6.5 | Keep dry and remove loose dust gently with a soft brush. Avoid soaking. Store separately and display away from strong sun and heat. |
| Celestite | SrSO₄ (Strontium Sulfate) | Orthorhombic (Tabular sky-blue crystals) | 3.0 – 3.5 (Fragile Geode Crystals) | Keep dry and remove loose dust gently with a soft brush. Avoid soaking. Store separately and display away from strong sun and heat. |
| Lepidolite | K(Li,Al)₃(Al,Si,Rb)₄O₁₀(F,OH)₂ (Lithium-bearing Mica) | Monoclinic (Layered flaky mica books or massive) | 2.5 – 3.5 (Soft Lilac Mica) | Keep dry and remove loose dust gently with a soft brush. Avoid soaking. Store separately and display away from strong sun and heat. |
| Smoky Quartz | SiO₂ (Natural irradiation of aluminum-bearing quartz) | Trigonal | 7.0 | Start with a soft, dry cloth. Check treatments, cracks and settings before using water. Store separately and display away from strong sun and heat. |
| Aquamarine | Be₃Al₂Si₆O₁₈ (Iron-colored Beryl) | Hexagonal | 7.5 – 8.0 (Durable Precious Beryl) | Start with a soft, dry cloth. Check treatments, cracks and settings before using water. Store separately and display away from strong sun and heat. |
| Almandine Garnet | Fe₃Al₂(SiO₄)₃ (Almandine) | Isometric (Natural Dodecahedrons) | 7.0 – 7.5 | Start with a soft, dry cloth. Check treatments, cracks and settings before using water. Store separately and display away from strong sun and heat. |
| Rhodonite | (Mn²⁺,Fe²⁺,Mg,Ca)SiO₃ (Manganese Inosilicate) | Triclinic | 5.5 – 6.5 | Keep dry and remove loose dust gently with a soft brush. Avoid soaking. Store separately and display away from strong sun and heat. |
| Shungite | Variable Carbon and Mineral Composition | Heterogeneous Rock (No Single Crystal System) | 3.5 – 4.0 | Keep dry and remove loose dust gently with a soft brush. Avoid soaking. Store separately and display away from strong sun and heat. |
| Peridot | (Mg,Fe)₂SiO₄ (Magnesium Iron Silicate) | Orthorhombic | 6.5 – 7.0 | Keep dry and remove loose dust gently with a soft brush. Avoid soaking. Store separately and display away from strong sun and heat. |
| Blue Kyanite | Al₂SiO₅ (Aluminum Silicate) | Triclinic (Elongated bladed crystals) | 4.5 parallel to blade / 7.0 across blade (Anisotropic) | Keep dry and remove loose dust gently with a soft brush. Avoid soaking. Store separately and display away from strong sun and heat. |
| Nephrite & Jadeite Jade | Ca₂(Mg,Fe)₅Si₈O₂₂(OH)₂ (Nephrite) / NaAlSi₂O₆ (Jadeite) | Monoclinic | 6.0 – 7.0 (Exceptionally Tough Interlocking Fibers) | Start with a soft, dry cloth. Check treatments, cracks and settings before using water. Store separately and display away from strong sun and heat. |
| Oregon & Golden Sunstone | (Ca,Na)((Al,Si)₂Si₂O₈) with Copper/Hematite platelets | Triclinic / Monoclinic | 6.0 – 6.5 | Keep dry and remove loose dust gently with a soft brush. Avoid soaking. Store separately and display away from strong sun and heat. |
| Hematite | Fe₂O₃ (Ferric Oxide — 70% Iron) | Trigonal (Specular metallic & botryoidal) | 5.5 – 6.5 | Keep dry and remove loose dust gently with a soft brush. Avoid soaking. Store separately and display away from strong sun and heat. |
| Amazonite | KAlSi₃O₈ (Potassium Feldspar) | Triclinic | 6.0 – 6.5 | Keep dry and remove loose dust gently with a soft brush. Avoid soaking. Store separately and display away from strong sun and heat. |
| Bloodstone (Heliotrope) | SiO₂ + Fe₂O₃ (Hematite inclusions) | Trigonal (Dark green jasper/chalcedony with red hematite spots) | 6.5 – 7.0 | Start with a soft, dry cloth. Check treatments, cracks and settings before using water. Store separately and display away from strong sun and heat. |
| Moldavite | SiO₂ (~80%) + Al₂O₃ + Lechatelierite inclusions | Amorphous (Impact Crater Silica Glass) | 5.5 – 6.0 | Start with a soft, dry cloth. Check treatments, cracks and settings before using water. Store separately and display away from strong sun and heat. |
| Sodalite | Na₈(Al₆Si₆O₂₄)Cl₂ (Sodium Aluminum Silicate Chloride) | Isometric | 5.5 – 6.0 | Keep dry and remove loose dust gently with a soft brush. Avoid soaking. Store separately and display away from strong sun and heat. |
| Red Jasper | SiO₂ + Fe₂O₃ | Trigonal (Microcrystalline Quartz with Hematite inclusions) | 6.5 – 7.0 | Start with a soft, dry cloth. Check treatments, cracks and settings before using water. Store separately and display away from strong sun and heat. |
| Chrysocolla | (Cu,Al)₂H₂Si₂O₅(OH)₄·nH₂O (Hydrated Copper Phyllosilicate) | Orthorhombic / Amorphous hydrogel | 2.5 – 3.5 (Up to 7.0 when silicified in Quartz/Chalcedony) | Keep dry and remove loose dust gently with a soft brush. Avoid soaking. Store separately and display away from strong sun and heat. |
| Rhodochrosite | MnCO₃ (Manganese Carbonate) | Trigonal (Banded stalactitic & rhombohedral) | 3.5 – 4.0 (Soft Carbonate — Handle Gently) | Keep dry and remove loose dust gently with a soft brush. Avoid soaking. Store separately and display away from strong sun and heat. |
| Black Kyanite | Al₂SiO₅ (Graphite/Iron-included Aluminum Silicate) | Triclinic (Radiating broom-like fans) | 4.5 – 7.0 (Anisotropic Bladed Fans) | Keep dry and remove loose dust gently with a soft brush. Avoid soaking. Store separately and display away from strong sun and heat. |
| Ametrine | SiO₂ (Differential oxidation of Fe²⁺/Fe³⁺ iron zones) | Trigonal (Color-zoned hexagonal prisms) | 7.0 | Start with a soft, dry cloth. Check treatments, cracks and settings before using water. Store separately and display away from strong sun and heat. |
| Rainbow Hopper Bismuth | Bi (Atomic Number 83 — Oxide Thin-Film Iridescence) | Rhombohedral / Trigonal (Skeletal 'Hopper' Growth) | 2.25 (Brittle Metallic Hopper Steps) | Keep dry and remove loose dust gently with a soft brush. Avoid soaking. Store separately and display away from strong sun and heat. |
| Peacock Ore (Bornite & Chalcopyrite) | Cu₅FeS₄ (Bornite) / CuFeS₂ (Tarnished Chalcopyrite) | Orthorhombic / Tetragonal | 3.0 – 4.0 | Keep dry and remove loose dust gently with a soft brush. Avoid soaking. Store separately and display away from strong sun and heat. |
| Angelite (Blue Anhydrite) | CaSO₄ (Anhydrous Calcium Sulfate) | Orthorhombic (Massive powder-blue nodules) | 3.5 (Soft Sulfate — Keep Dry) | Keep dry and remove loose dust gently with a soft brush. Avoid soaking. Store separately and display away from strong sun and heat. |
| Lilac Kunzite | LiAlSi₂O₆ (Manganese-colored Lithium Aluminum Silicate) | Monoclinic (Vertically striated flat blades) | 6.5 – 7.0 (Perfect prismatic cleavage — handle gently) | Keep dry and remove loose dust gently with a soft brush. Avoid soaking. Store separately and display away from strong sun and heat. |
| Larimar | NaCa₂Si₃O₈(OH) (Copper-substituted Sodium Calcium Silicate) | Triclinic (Radiating needle aggregates) | 4.5 – 5.0 (Up to 6.0 in dense blue centers) | Keep dry and remove loose dust gently with a soft brush. Avoid soaking. Store separately and display away from strong sun and heat. |
| Natural Turquoise | CuAl₆(PO₄)₄(OH)₈·4H₂O (Hydrated Copper Aluminum Phosphate) | Triclinic (Cryptocrystalline nodules & veins) | 5.0 – 6.0 (Porous Phosphate) | Keep dry and remove loose dust gently with a soft brush. Avoid soaking. Store separately and display away from strong sun and heat. |
| Moss Agate | SiO₂ + Fe/Mg silicate inclusions | Trigonal (Translucent chalcedony with green hornblende/chlorite dendrites) | 6.5 – 7.0 | Start with a soft, dry cloth. Check treatments, cracks and settings before using water. Store separately and display away from strong sun and heat. |
| Blue Lace Agate | SiO₂ (Microcrystalline banded quartz) | Trigonal (Finely banded periwinkle-blue chalcedony) | 6.5 – 7.0 | Start with a soft, dry cloth. Check treatments, cracks and settings before using water. Store separately and display away from strong sun and heat. |
| Bumblebee Jasper (Volcanic Calcite) | CaCO₃ + Sulfur + Manganese Oxide + Orpiment (As₂S₃) | Trigonal / Monoclinic Aggregate | 4.5 – 5.0 | Keep dry and remove loose dust gently with a soft brush. Avoid soaking. Store separately and display away from strong sun and heat. |
| Unakite | Ca₂(Al,Fe)₃(SiO₄)₃(OH) + KAlSi₃O₈ + SiO₂ | Monoclinic / Triclinic Aggregate (Epidote + Orthoclase + Quartz) | 6.0 – 7.0 | Start with a soft, dry cloth. Check treatments, cracks and settings before using water. Store separately and display away from strong sun and heat. |
| Kambaba Jasper (Eldarite) | SiO₂ + NaFe³⁺Si₂O₆ (Aegirine/Amphibole orbicular swirls) | Trigonal / Microcrystalline Quartz & Aegirine orbs | 6.5 – 7.0 | Start with a soft, dry cloth. Check treatments, cracks and settings before using water. Store separately and display away from strong sun and heat. |
| Saharan Desert Rose Selenite | CaSO₄·2H₂O + Quartz Sand Inclusions | Monoclinic (Lenticular rosette twin blades) | 2.0 (Fragile Sand-Gypsum Petals) | Keep dry and remove loose dust gently with a soft brush. Avoid soaking. Store separately and display away from strong sun and heat. |
| Apache Tear Obsidian | SiO₂ (70%+ Rhyolitic Glass) | Amorphous (Rounded sub-vitreous volcanic glass nodules) | 5.0 – 5.5 | Start with a soft, dry cloth. Check treatments, cracks and settings before using water. Store separately and display away from strong sun and heat. |
Hardness & Care Questions
What does the Mohs hardness value mean?
Mohs hardness compares scratch resistance. It does not measure resistance to breaking, establish water compatibility or identify an individual specimen. Store pieces separately, including those with similar hardness.
How do I use the care column?
Use the care note as a cautious starting point. Check the actual piece for treatments, cracks, coatings and jewelry settings before wet cleaning. Avoid salt soaks and strong sunlight; ask a specialist before using steam or ultrasonic cleaning.