Silica is prepared by the hydrolysis of silicon tetrachloride with water and heating the hydrated oxide formed. It's a transparent solid with a high melting point.

Silica is inert to most chemical reagents but reacts with hydrogen fluoride to form silicon tetrafluoride, which is a colourless gas at room temperature and water.

Silica is an acidic oxide, which reacts with alkalis to form salt and water.

When silica is mixed with solid sodium carbonate and melted, sodium silicate is formed. This reaction is the basic reaction in the manufacture of glass.

Cement is a complex aluminum silicate. Its strength is due to the strong bonding of the SiO4 groups.

Quartz silica can have colourless or white, black, purple, or green crystals. It is odourless and will not burn. Quartz silica is an occupational CANCER HAZARD - can cause cancer.

With all this in mind. The plan to kill a person using a complex array of traps that are formed from different variations on silica is made quite easy.

1. First, you must make a three walled contraption out of very thick glass, (a silica type of glass!). It must have hinges. Make sure there is a 6"-1' deep floor area with quick-drying cement in the bottom of it.
2. Lure somebody into the contraption with pretty black and white crystals
3. Close the contraption by pushing one of the walls to.
4. Add a ceiling to the contraption and begin to let silicon tetraflouride seep in, suffocating the victim while the cement dries.
5. Afterwards, pour saltwater into the contraption (saltwater that you made with SILICA!!!).
6. Freeze it (breaking the glass).
7. Set it up in a refrigerated room on public display to serve as a warning to those who would cross you.

Never trust a person who has mastery in the deadly art of Silica.

Silicon is the only element besides carbon that chemists have coerced into forming complex chains and molecules. Hence, some scientists have hypothesized that the only complex biological life-forms possible besides carbon-based lifeforms would be silica-based lifeforms (to speak nothing of electronic post-biological silicon lifeforms).

Professor Pi tells me that boron also forms complex polymers called borates, but boron is less abundant than silicon.