Identifying Red and Pink Minerals

## Red and Pink Color Origins

Red in minerals typically results from chromium, iron, or manganese in the crystal lattice. Pink is often a dilute version of the same chromophores. Some reds come from inclusions (rutilated quartz) or structural effects.

## Step 1: Streak Test

Streak color is the most important first test for red minerals.

| Streak | Candidates |
|--------|------------|
| Red | Hematite (despite metallic gray appearance!), cinnabar, cuprite |
| White/pale | Most silicates and phosphates |
| Orange-yellow | Realgar |
| Pink | Rhodonite powder |

## Step 2: Hardness-Based Identification

### Hard Red/Pink Minerals (Mohs 7+)

| Mineral | Formula | Mohs | Crystal System | Diagnostic |
|---------|---------|------|----------------|------------|
| Ruby (corundum) | Al₂O₃+Cr | 9 | Trigonal | Hexagonal prisms, adamantine luster |
| Red garnet (almandine) | Fe₃Al₂(SiO₄)₃ | 7–7.5 | Cubic | Dodecahedral crystals, no cleavage |
| Red garnet (pyrope) | Mg₃Al₂(SiO₄)₃ | 7–7.5 | Cubic | Deep red, in kimberlites |
| Spinel | MgAl₂O₄ | 7.5–8 | Cubic | Octahedral crystals, hard |
| Rose quartz | SiO₂+Ti/Mn | 7 | Trigonal | Massive (rarely forms crystals), translucent |

### Medium Red/Pink Minerals (Mohs 4–7)

| Mineral | Formula | Mohs | Crystal System | Diagnostic |
|---------|---------|------|----------------|------------|
| Rhodonite | MnSiO₃ | 5.5–6.5 | Triclinic | Pink with black MnO veins |
| Rhodochrosite | MnCO₃ | 3.5–4 | Trigonal | Banded pink, fizzes in warm acid |
| Spessartine garnet | Mn₃Al₂(SiO₄)₃ | 7–7.5 | Cubic | Orange-red, in pegmatites |
| Pink tourmaline | Na(Li,Al)₃Al₆Si₆O₁₈(BO₃)₃(OH)₄ | 7–7.5 | Trigonal | Prismatic, striated, triangular cross-section |

### Soft Red Minerals (Mohs < 4)

| Mineral | Formula | Mohs | Crystal System | Diagnostic |
|---------|---------|------|----------------|------------|
| Cinnabar | HgS | 2–2.5 | Trigonal | Bright red, very heavy (SG 8.1), TOXIC |
| Realgar | As₄S₄ | 1.5–2 | Monoclinic | Orange-red, resinous, TOXIC, light-sensitive |
| Cuprite | Cu₂O | 3.5–4 | Cubic | Deep red, adamantine, in copper deposits |
| Crocoite | PbCrO₄ | 2.5–3 | Monoclinic | Bright orange-red prismatic crystals |
| Proustite | Ag₃AsS₃ | 2–2.5 | Trigonal | "Ruby silver," translucent red, light-sensitive |

## Danger Minerals

Several red minerals are toxic. Handle with care:

- **Cinnabar** (HgS): Mercury compound — do not heat or inhale dust
- **Realgar** (As₄S₄): Arsenic compound — wash hands, store in dark
- **Crocoite** (PbCrO₄): Lead and chromium — wash hands after handling

## Quick Identification Summary

- Red streak despite gray color → Hematite
- Pink + black veins → Rhodonite
- Pink + banded + fizzes → Rhodochrosite
- Deep red + dodecahedral → Garnet
- Bright red + very heavy → Cinnabar