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Typical Price Tiers (per piece)
Entry
$10+
Mid-tier
$100+
Premium
$1,000+
Investment
$10,000+
Specimen tier. Elmwood / Brazilian classics. Twin habits premium.
Approximate retail prices. Wholesale + private sale typically 40-60% of retail. Auction premium 10-25%. For investment-grade purchase steps, see the investment checklist.
Crystal Structure
Trigonal carbonate — CO₃²⁻ groups stacked normal to c-axis.
External databases provide CIF (Crystallographic Information File) downloads + interactive 3D viewers. AMCSD: American Mineralogist Crystal Structure Database (free, RRUFF-hosted). COD: open community-curated database.
Elemental Composition (by mass)
| Element | Mass % | Visual |
|---|---|---|
| O Oxygen | 47.96% | |
| Ca Calcium | 40.04% | |
| C Carbon | 12.00% |
Computed from simplified end-member formula. Solid-solution series, water content, and trace substitutions cause real-world variation.
Reference Resources
- Most-documented mineral on Mindat (1000+ localities)
IMA Abbreviation (Whitney-Evans 2010)
Cal
→ Calcite
Carbonate — most common
Standard symbol from American Mineralogist (Whitney & Evans, 2010). Used in thin-section labeling, phase diagrams, and IMA-style species records.
Pronunciation
/ˈkælsaɪt/
↔ KAL-site
Latin calx (lime)
⚠ Safety & Handling
⚗acid-sensitivehigh
Dissolves in even dilute acids — including white vinegar.
Handling: Never use ANY acid cleaner. Distilled water OK for brief rinse. pH-neutral specimen cleaners only.
Information provided in good faith. Consult local hazmat regulations for transport and disposal. Severely hazardous specimens may require special storage cabinets.
UV Fluorescence
SW (254 nm)
Red / orange
strong
LW (365 nm)
Red / orange
moderate
Mn-activated calcite; Franklin variety especially bright. Red SW + green willemite makes the Franklin "two-color" effect.
SW = shortwave (germicidal lamp). LW = longwave (blacklight). Response varies with locality, trace impurities, and treatment.
Pseudomorph Relationships
Replaced by — this mineral commonly becomes:
→ Quartz replacement
Cone-shaped quartz pseudomorphs after scalenohedral calcite — sometimes called "babingtonite".
Cornwall; Bohemia.
Replaces — this mineral is often a pseudomorph after:
← Aragonite inversion
Aragonite transforms to calcite over geological time — most older shells are now calcite pseudomorphs.
Universal in older limestones.
A pseudomorph (Greek "false form") is a mineral with the external shape of another species — the chemistry has changed but the crystal habit is inherited. › Full catalogue
Tenacity
Behavior:
brittle
Under stress:
Cleaves into rhombs
Rhombohedral cleavage — taps produce small rhombs.
Luster
vitreous
Glassy.
Notable localities (coordinates)
- Franklin / Sterling Hill — New Jersey, USA41.1200, -74.5800 › OpenStreetMap
- Dalnegorsk — Primorsky Krai, Russia44.5500, 135.5800 › OpenStreetMap
All localities and full GeoJSON available at /wp-json/mmb/v1/localities-geo
Diaphaneity (Transparency)
transparent-to-translucent
Iceland spar is famously transparent (double refraction).
Magnetism
Category:
diamagnetic
Test result:
Slight repulsion
CaCO₃ — historically used by Faraday to demonstrate diamagnetism.
Test with rare-earth magnet (N42 or N52 neodymium). Suspend specimen on thread for sensitive paramagnetic detection. Diamagnetic minerals are weakly repelled (visible only with strong magnets like bismuth).
Diagnostic Field Tests
HCl test→ Vigorous effervescence (CO₂)
Cold dilute HCl on fresh surface fizzes immediately. Diagnostic for calcite.
Cleavage test→ Perfect rhombohedral cleavage
Tap with steel point — rhombs split cleanly.
⚠ Use dilute HCl (~10%) only on inconspicuous spots; rinse promptly. Smell-tests should be brief and ventilated. Taste-test ONLY halite/sylvite — never lead, arsenic, or sulfur minerals.
Specific Gravity
2.71–2.72
g/cm³
light
CaCO₃; standard carbonate reference.
For comparison: water = 1.00, glass ≈ 2.5, quartz = 2.65, corundum ≈ 4.00, galena ≈ 7.50, gold ≈ 19.3.
Streak Test
white
White streak. Fizzes in cold HCl.
Streak = color of the powdered mineral. Drag specimen across unglazed white porcelain plate (Mohs 6.5). For minerals harder than the plate, crush a small flake into powder and observe color.
Geological Setting
Environment:
multiple
Host rock:
limestone, marble, hydrothermal vein, cave speleothem
Companions:
Forms by primary precipitation in marine settings, late-stage hydrothermal, or speleothem deposition.
Twinning Laws
e-twin {0118}lamellar
Lamellar twinning visible under polarized light; can be glide-twin induced by stress.
Butterfly twincontact
Two scalenohedra in heart/butterfly shape.
Care notesDistilled water + soft brush. Avoid acids (vinegar, lemon juice) — they dissolve calcite immediately. Full cleaning guide →
★★★★★5 / 5 based on 12 customer reviews across 77 specimens
Cleavage & Fracture
Cleavage:
perfect 3 directions {1011} — rhombohedral
Fracture:
conchoidal
Rhombohedral cleavage. Cleavage rhombs are diagnostic.
Market availability: Common
Widely available in most dealer stocks. Specimens span all price tiers.
Collector tier: Cabinet Classic
World-class display species — sought after for cabinet collections, well-documented localities, frequent show-piece pieces.
PolymorphsShares the formula
CaCO3 with: Aragonite · Vaterite — same chemistry, different crystal structure.Mohs 3
Vickers (~) 170 HV
Knoop (~) 185 HK
Nickel–Strunz
5.AB.05Dana
14.01.01.01Geological setting
MetamorphicSedimentary
Diagnostic properties
Strong birefringence
Element composition by mass
Formula: CaCO₃ · molar mass: 100.09 g/mol
| O | 47.96% | |
| Ca | 40.04% | |
| C | 12% |
Computed from atomic weights (IUPAC 2021). Site-occupancy groups (Fe,Mn) split equally.
Mohs Hardness
3
Calcite sits at 3 on the Mohs scale — can be scratched by a steel knife.
Colors:
Streak
White
White
Crystal system
Trigonal
Trigonal
Pronunciation/ˈkælsaɪt/
Type localityIceland (Eskifjörður, Iceland spar)
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CarbonatesCarbonates
TL;DR · 1 min read
Text size:AAA
Calcite is the workhorse of the carbonate world — common, but capable of producing some of the most spectacular crystal habits in mineralogy. Chinese calcites from Hunan and Hubei rank among the largest and most aesthetic ever recovered.
Notable Varieties #
- Iceland Spar (clear, double-refracting)
- Manganocalcite (Mn-bearing pink)
- Cobaltocalcite (deep magenta, Co-bearing)
- Stalactitic / banded onyx-marble
The Chinese Angle #
Daye and Tonglushan mines in Hubei have produced museum-quality golden scalenohedral calcite crystals exceeding 30 cm. The Shangbao Mine in Hunan is famous for translucent orange "tooth" calcites perched on pyrite or fluorite matrices.
Test at home — what scratches what
Will scratch your specimen:
🪙 Copper coin (US penny) (Mohs 3.5) · 🔪 Steel pocket knife (soft steel) (Mohs 5) · 🥃 Glass plate (Mohs 5.5) · 🔧 Steel file / hardened steel (Mohs 6.5) · ⚙ Sharp steel needle / quartz scratch (Mohs 7) · 🪨 Topaz scratch test (Mohs 8)
🪙 Copper coin (US penny) (Mohs 3.5) · 🔪 Steel pocket knife (soft steel) (Mohs 5) · 🥃 Glass plate (Mohs 5.5) · 🔧 Steel file / hardened steel (Mohs 6.5) · ⚙ Sharp steel needle / quartz scratch (Mohs 7) · 🪨 Topaz scratch test (Mohs 8)
Your specimen will scratch:
👆 Talc dust (Mohs 1) · 💅 Fingernail (Mohs 2.5)
👆 Talc dust (Mohs 1) · 💅 Fingernail (Mohs 2.5)
Always test on an inconspicuous edge first. Save the test for unimportant specimens — better to use a streak plate or knowledge of locality + paragenesis.
Cite this entry
APA
MyMineralBox Editorial Team. (2026). Calcite. My Mineral Box. Retrieved May 23, 2026, from https://mymineralbox.com/mineral-encyclopedia/minerals/calcite/
MLA
MyMineralBox Editorial Team. "Calcite." My Mineral Box, 2026, https://mymineralbox.com/mineral-encyclopedia/minerals/calcite/. Accessed May 23, 2026.
Chicago
MyMineralBox Editorial Team. "Calcite." My Mineral Box. Last modified May 4, 2026. https://mymineralbox.com/mineral-encyclopedia/minerals/calcite/.
BibTeX
@misc{mmb_calcite,
author = {{MyMineralBox Editorial Team}},
title = {{Calcite}},
year = {2026},
publisher = {My Mineral Box},
url = {https://mymineralbox.com/mineral-encyclopedia/minerals/calcite/},
urldate = {2026-05-23}
}
