硬度、条痕、光沢、劈開、結晶癖、簡易化学テストを用いた鉱物と鉱石のフィールド 同定。体系的消去法、モース硬度計の適用、貴金属・宝石・工業用鉱物の一般的な 鉱石指標を網羅する。未知の岩石や鉱物標本に遭遇した時、探鉱中にサイトが価値ある 鉱物指標を示すかどうかを評価する時、フィールドで鉱石を含む岩石を不毛の岩石と 区別する時、または体系的な観察を通じて地質学的リテラシーを構築する時に使用する。
物理的性質、体系的消去法、簡易フィールドテストを用いてフィールドで鉱物を同定する。
取り扱う前に、標本を文脈の中で観察する。
Field Context:
+--------------------+------------------------------------------+
| Observation | Record |
+--------------------+------------------------------------------+
| Host rock | What type of rock is it in/on? |
| | (granite, basite, sandstone, schist...) |
+--------------------+------------------------------------------+
| Geological setting | Vein, disseminated, massive, placer, |
| | weathering surface, cave deposit |
+--------------------+------------------------------------------+
| Associated | What other minerals are nearby? |
| minerals | (quartz veins often host gold; iron |
| | staining suggests oxidation zone) |
+--------------------+------------------------------------------+
| Crystal form | Visible crystals? Habit? Size? |
| (if visible) | (cubic, prismatic, tabular, massive) |
+--------------------+------------------------------------------+
期待結果: 標本を取り扱う前にフィールドコンテキストが記録されていること。
失敗時: 地質学的コンテキストが不明な場合（遊離標本、都市部での発見）、物理的性質のみで進める — コンテキストは候補を絞るのに役立つが、厳密には必須ではない。
診断テストを体系的に適用する。
Diagnostic Property Tests:
LUSTER (how it reflects light):
- Metallic: reflects like metal (pyrite, galena, gold)
- Vitreous: glassy (quartz, feldspar)
- Pearly: like a pearl (muscovite, talc surfaces)
- Silky: like silk fibers (asbestos, satin spar gypsum)
- Earthy/dull: no reflection (kaolin, limonite)
- Adamantine: brilliant, diamond-like (diamond, zircon)
HARDNESS (Mohs scale — scratch test):
+------+-----------+----------------------------------+
| Mohs | Reference | Can Be Scratched By |
+------+-----------+----------------------------------+
| 1 | Talc | Fingernail |
| 2 | Gypsum | Fingernail (barely) |
| 3 | Calcite | Copper coin |
| 4 | Fluorite | Steel nail (easily) |
| 5 | Apatite | Steel nail (just) |
| 6 | Feldspar | Steel nail cannot scratch |
| 7 | Quartz | Scratches glass |
| 8 | Topaz | Scratches quartz |
| 9 | Corundum | Scratches topaz |
| 10 | Diamond | Scratches everything |
+------+-----------+----------------------------------+
Test: try to scratch the specimen with each reference tool,
starting from soft to hard. The hardness is between the tool
that fails and the tool that succeeds.
STREAK (powder colour on porcelain):
- Drag the specimen firmly across an unglazed porcelain tile
- Record the colour of the powder line
- Streak colour is often different from specimen colour
- Critical: hematite is grey-black but streaks RED
- Critical: pyrite is gold but streaks BLACK
- Minerals harder than the streak plate (~7) will not leave a streak
CLEAVAGE AND FRACTURE:
- Cleavage: breaks along flat planes (mica: 1 direction, feldspar: 2)
- Fracture: breaks irregularly (conchoidal = curved like glass, uneven, fibrous)
- Note number of cleavage directions and angles between them
SPECIFIC GRAVITY (heft test):
- Hold the specimen and assess: does it feel heavier or lighter
than expected for its size?
- Heavy: possible metallic ore (galena, gold, magnetite)
- Light: possible pumice, sulfur, or organic material
期待結果: 標本のプロファイル: 光沢、硬度範囲、条痕色、劈開/断口タイプ、相対密度。
失敗時: 性質が曖昧な場合（例: 金属光沢とガラス光沢の間 — 「亜金属」）、両方の選択肢を記録する。曖昧さは確信度を下げるが、同定を妨げない。
特定の鉱物グループに対する追加テスト。
Special Field Tests:
MAGNETISM:
- Hold a magnet near the specimen
- Strong attraction: magnetite (or possibly pyrrhotite)
- Weak attraction: some iron-bearing minerals
ACID TEST (10% HCl):
- Drop acid on the specimen surface
- Vigorous fizzing: calcite (CaCO3)
- Fizzing on powder only: dolomite (scratch surface first, then apply acid)
- No fizzing: not a carbonate
TASTE (only for suspected halite):
- Salty taste: halite (NaCl)
- Do NOT taste unknown minerals generally — some are toxic
SMELL:
- Sulfur: rotten egg smell (sulfides when scratched)
- Clay: earthy "petrichor" smell when breathed on (clay minerals)
TENACITY:
- Brittle: shatters when struck (most silicates)
- Malleable: deforms without breaking (gold, copper, silver)
- Flexible: bends and stays (chlorite, some micas)
- Elastic: bends and springs back (muscovite mica)
期待結果: 同定をさらに絞り込む追加の診断データ。
失敗時: 特殊テストが利用できない場合（磁石がない、酸がない）、基本的な性質で進める — ほとんどの一般的な鉱物にはそれで十分である。
性質プロファイルを既知の鉱物と照合する。
Common Mineral Identification Key (simplified):
METALLIC LUSTER:
- Black streak + hard (6+) + cubic crystals = PYRITE
- Black streak + soft (2.5) + heavy + cubic = GALENA
- Red-brown streak + hard (5-6) + heavy = HEMATITE
- Yellow streak + soft (1.5-2.5) + yellow = GOLD (if malleable)
or CHALCOPYRITE (if brittle, harder, green-black streak)
- Black streak + magnetic = MAGNETITE
NON-METALLIC, LIGHT-COLORED:
- Vitreous + hard (7) + conchoidal fracture = QUARTZ
- Vitreous + hard (6) + 2 cleavage planes = FELDSPAR
- Vitreous + soft (3) + fizzes in acid = CALCITE
- Pearly + very soft (1) + greasy feel = TALC
- Vitreous + soft (2) + 1 perfect cleavage = GYPSUM
NON-METALLIC, DARK-COLORED:
- Vitreous + hard (5-6) + 2 cleavage at ~90 degrees = PYROXENE
- Vitreous + hard (5-6) + 2 cleavage at ~60/120 degrees = AMPHIBOLE
- Vitreous + soft (2.5-3) + 1 perfect cleavage + flexible = BIOTITE (mica)
期待結果: 鉱物の同定、または2-3の候補のショートリストと、それらを区別するために必要な判別テスト。
失敗時: 標本が一般的な鉱物のいずれとも一致しない場合、単一の鉱物ではなく岩石（鉱物の集合体）である可能性があるか、実験室分析（薄片、XRD）が必要な場合がある。
gold-washing — 沖積金の回収は、河川堆積物を読み取り金を含む砂利を評価するために鉱物同定スキルを使用する