The molecular formula of Magnesium hexafluorosilicate(18972-56-0) is  F₆H₁₂MgO₆Si and its formula weight is 274.47.
Magnesium hexafluorosilicate(18972-56-0) has a  melting point of   120°C (dec.).
The chemical synonyms of Magnesium hexafluorosilicate(18972-56-0) are eulavasm;fluosilicatedemagnesium;MagnesiumfluosilicateHexahyd;Magnesiumhexafluorosilicate(2-)hexahydrate;Magnesiumsiliconhexafluoridehexahydrate;Silicate(2-),hexafluoro-,magnesium,hexahydrate;MAGNESIUM SILICOFLUORIDE;MAGNESIUM SILICOFLUORIDE HEXAHYDRATE
The molecular structure of Magnesium hexafluorosilicate(18972-56-0):

Poison by ingestion. Moderately toxic by subcutaneous route. When heated to decomposition it emits toxic fumes of F⁻. See also FLUORIDES and MAGNESIUM COMPOUNDS.
Risk Statements  25
Safety Statements  24/25-45
RIDADR  2853
HazardClass  6.1
PackingGroup  III

OSHA PEL: TWA 2.5 mg(F)/m³
ACGIH TLV: TWA 2.5 mg(F)/m³; BEI: 3 mg/g creatinine of fluorides in urine prior to shift; 10 mg/g creatinine of fluorides in urine at end of shift.
NIOSH REL: TWA 2.5 mg(F)/m³

Storage
Store in a cool, dry location in a tightly sealed container. Corrosive area.
Handling
All chemicals should be considered hazardous. Avoid direct physical contact. Use appropriate, approved safety equipment. Untrained individuals should not handle this chemical or its container. Handling should occur in a chemical fume hood.
Incompatibilities
Reacts with acids evolving HF and SiF4, irritating and corrosive gases.
Combustion Products
Fire may produce irritating, corrosive and/or toxic gases.