Swinefordite is a rare lithium-bearing member of the smectite group of clay minerals. It typically occurs as soft, massive, or clay-like aggregates, often found as a alteration product in hydrothermal environments.
Is this swinefordite?
5-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry to scratch swinefordite with a known reference. Swinefordite sits at Mohs ~1, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: glistening when hydrated; dull when partially dehydrated.
- 4Match the color rangeCompare against the expected color range: greenish gray, light olive green.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: aggregates.
Often confused with
Swinefordite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Luster reads glistening when hydrated; dull when partially dehydrated on Swinefordite and dull, earthy on Montmorillonite.
How to tell apart: Luster reads glistening when hydrated; dull when partially dehydrated on Swinefordite and greasy on Saponite.
How to tell apart: Luster reads glistening when hydrated; dull when partially dehydrated on Swinefordite and pearly, greasy, dull on Talc.
Often found alongside swinefordite
Minerals reported to co-occur with swinefordite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca₀.₂(Li,Al,Mg,Fe,Fe)₃(Si,Al)₄O₁₀(OH,F)₂·nH₂O
- Mohs hardness
- ~1
- Density
- 2.3-2.8 g/cm³
- Colors
- Greenish grayLight olive green
- Streak
- White
- Luster
- Glistening when hydrated; dull when partially dehydrated
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Aggregates
- Cleavage
- Perfect on {001}
- Rarity
- Rare
- Uses
- Collector, Scientific research
- Host rock
- Deposited from ground water, as coatings on the walls of fracture zones and fissures, or replacing spodumene, in a Li-Sn-rich pegmatite
Where rockhounds find swinefordite
Classic worldwide localities
- Foote mine, Kings Mountain, Cleveland Co., North Carolina, USA
Field-hunting tip
Where it forms: Deposited from ground water, as coatings on the walls of fracture zones and fissures, or replacing spodumene, in a Li-Sn-rich pegmatite. If you start seeing spodumene, switzerite, vivianite in float, you are in the right ground. Typical habit: aggregates. Train your eye for that shape before scanning the outcrop.
Common questions
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Find swinefordite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
