It's a little more complicated than that...

high pressure mercury vapor lamps have an inner fused arc tube made of silica that is nearly impossible to crush... that arc tube is then sealed inside of the outer vacuum chamber

the arc tube is stimulated by trimetallic operating diodes which cause electrical impulses and resonate with the mercury vapor inside the high pressure tube causing an intense heat/radiating effect

you cannot drop one and have mercury vapor spill out!! there is a trace amount inside the arc tube and it is very hard to crush
-----