Potassium tris(oxalato) aluminate

Formula: K₃[Al(C₂O₂)₃]·3H₂O

Also known as potassium alumooxalate or potassium oxalatoaluminate. Similar compounds:

Sodium analog that have different structure: sodium tris(oxalato) aluminate.
Iron analog, with the same structure and nice green color: potassium tris(oxalato) ferrate(III).

Potassium Alum

Formula: KAl(SO₄)₂·12H₂O Iconic compound for crystal growing.

Formula: NH₄Al(SO₄)₂·12H₂O

The biggest specimen in my collection. Mass is 45g, growth time is 4 months.