Lecontite

Lecontite (sodium ammonium sulfate dihydrate, with potassium substituting for some ammonium, typically about a fourth^[2]) is a sulfate mineral with the formula (NH₄,K)NaSO₄·2H₂O. It was found by John Lawrence LeConte in Las Piedras Cave in Honduras as a breakdown product of bat guano, including crystals up to an inch long^[3] and identified as a separate mineral by W.J. Taylor in 1858.^[4] As of 1963 most natural specimens came from the same cave.^[5]

Lecontite
General
Category	Sulfate mineral
Formula	(NH4,K)NaSO4·2H2O
IMA symbol	Lcn[1]
Strunz classification	7.CD.15
Crystal system	Orthorhombic
Identification
Color	Colorless
Cleavage	{011} Distinct [2]
Mohs scale hardness	2–2.5
Luster	Vitreous to dull
Streak	White
Diaphaneity	Transparent to translucent
Specific gravity	1.745 g/cc[3]
Density	1.745 g/cc
Refractive index	nα = 1.440 nβ = 1.454 nγ = 1.455[3]
Birefringence	δ = 0.015[3]

Lecontite can easily be synthesized by reacting ammonium sulfate with sodium sulfate in aqueous solution and crystallized.^[6]