Upon first sight of their portion in the Holy Land, the tribe of Zebulun was appalled. “It’s all sand,” they complained to the Creator! “There’s nothing here but sand! And salt water…sand and sea! What kind of portion is that?”
A most excellent portion, as it turned out. The clean, bright sand of the Mediterranean beach became the ancient world’s best source for highly prized, clear, colorless glass. The Sea itself provided a highway for commerce. Merchant ships of Zebulun sailed forth carrying glass and other good to ports throughout the region. With their profits they supported the tribe of Issachar so the latter could engage, without interruption, in scholarly study of the Torah.[1]
But their observation, “It’s all sand!” had substance. In fact, those words could almost be said of the whole earth’s surface. That’s because more than ninety percent of the earth’s crust is made of the same stuff that sand is made of: the elements silicon and oxygen.[2] Silicon is a brittle gray metalloid and oxygen is the colorless gas that we breathe to stay alive. But when these two elements combine they form silicates, and silicates are everywhere under our feet.
The fundamental silicate unit is shaped like a tetrahedron. That’s a geometric solid with four triangular faces. As a chemical form, a silicon atom sits in the middle, bound to four oxygen atoms, one on each corner. The bonds are covalent, consisting of electrons shared between the silicon atom and its four oxygen neighbors. They are also highly directional. Therefore, silicates are rigid, unlikely to bend under force, much more likely to crack or shatter.
Tetrahedron: Geometric left, and silicate,right
Silicate tetrahedra can stand alone, or they can link up in chains, sheets or three-dimensional networks. The possible arrangements are almost infinite. Add in the presence of other elements, particularly metal atoms like aluminum, iron, magnesium, or even less common metals like manganese or chromium, and you can begin to imagine the vast number of possible silicate compounds.[3]
Silicates in chains and sheets.
Most silicates make up plain old rocks. (Geologists, forgive me! Those rocks may be old, but to one who understands them, they are far from plain.) Other silicates form gemstones like topaz, garnet, jade, and lapis lazuli. It all depends on how the silicon dioxide units are arranged and which extra elements perch among them.
For example, the beautiful crystals of quartz are a silicate network. Each oxygen atom bonds to two silicon atoms, giving quartz the formula SiO2, silicon dioxide. Sand is mainly finely crushed quartz.
Crystals of quartz, pure silicon dioxide. CanStock photo by Martinan
Add some aluminum atoms to the silicon dioxide network, spike it with a few other elements like sodium, calcium, potassium, and so on, and you have the vast class of rocks called feldspars. Arrange the silicate units into sheets and you have, among other minerals, shiny, flaky mica. Bind water molecules between silicate sheets and you have clay, for pottery and thousands of other uses, both ancient and modern. Even asbestos, a mineral whose long crystals look like bundles of fibers, is a silicate. Its tetrahedral units link together in chains. In the science of crystals, the macroscopic form often hints at the microscopic arrangement of atoms.
Why did G-d create all this variety and profusion?
Everything that the Holy-One-Blessed-is-He created in His world, He created only for His Honor—Pirkei Avot, 6:11.
The Holy Temple in Jerusalem represented G-d’s honor to all observers. Its rituals and splendor implied dignity and order, a counterpoint to life’s frequently messy struggles. Not least among the splendid items was the breastplate of the High Priest. The twelve jewels arranged on it represented the twelve tribes of Israel. Most of these jewels were silicates.
Silicates are as common as sand, and as rare as carnelian or topaz. But wherever you look, the basic matter of the earth anticipates its ultimate holy purpose. That is to remind humanity of the omnipresent creative force we call G-d.
[1] All the material up to this note (i.e. first two paragraphs) are from Rashi commentary on Deuteronomy 33:19
[2]Editors of Encyclopedia Britannica, Silicate Mineral, https://www.britannica.com/science/silicate-mineral, retrieved August 13, 2018.
[3] Anne E. Eggar, The Silicate Minerals, https://www.visionlearning.com/en/library/Earth-Science/6/The-Silicate-Minerals/140, retrieved August 7, 2018.