What are you doing wrecking fossils?
Carbonates fizz when exposed to acid, and bicarbonates especially fizz. The acid liberates the carbonate ion, which then dissociates into carbon dioxide and water.The water remains liquid, but the carbon dioxide turns into gas.The crystals are residue left behind. The red is probably hematite (rust). I don't know what the white is, likely quartz (silicon dioxide).
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