Reggie Murphy, age 10, of Fredericton, NTT; for his question;
What are opals made from?
A few weeks ago Andy answered a question about quartz, the most common mineral in the world. Opal is n special form of this plentiful material. Sizeable opals are often vary beautiful but never vary plentiful. And, whose stones are very beautiful and very rare, they rate as gems. Certain fine opals rate as gems, or precious stones.
The ingredients in opal are silica, oxygen and water. The solid material is silicon dioxide, one pert silica to two parts oxygen. This is the composition of quartz. In opal, the solid material is mixed with up to ten percent water.
Opal tends to form where hot, acid water runs among silicate minerals. The silicates form a soft, jelly‑like mass which, when hardened, becomes glowing opal. For this reason we find opal near hot springs and in regions where old volcanos onto poured their steam, chemicals and soothing lava over the; earth.
Most precious stones are transparent, as clear as plain or colored glass. Opal is opaque, you cannot see through it. It occurs in sizeable lumps of no particular shape, in small nodules and in thin veins. Sometimes thin sheets of opal are found in the crevices of lava buds.
The colors of opal challenge the rainbow. And. the color has a lot to do with the value of opal. Precious opal, a gem stone, is multicolored. In the light the play of soft colors includes every abode you can imagine. Opals of this type are found in Hungary, Mexico and Queensland, Australia.
Fire opal is mother valunblo stone. Its colors are deeper and range from flame red through orange to soft yellows. Common opal has the rainbow colors though they are less vivid. than those in gem opa1.
Opal is built up in thin films, ono upon another. Light passing through these layers is boat, or refracted. 1'hcopal acts as a prism. This is what causes the lining to split and reveal its rainbow colors.
Andy has a lump of opal that you might never recognize. It is a pa1e, milky stone i th milky stone with what appear to be buried ridges. Magnified, these ridges look like woody cells. This is not surprising because Andy's opal is a bit of petrified wood.
A lot of petrified wood has become opal when the logs fell millions of years ago, there were silicates and acid waters in the soil. Those ingredients combined to replace the woody tissues with particles of opal.
Another surprising place to find opal is in the kitchen. And, of all things, we use it to clean the sink. Cleansing powder is mode from diatomaeqous earth which was made by diatoms. Diatoms, of course, are tiny one‑celled plants which teem in seas end rivers. These plants make themselves tiny shells, or houses end these little homes are made of opal.
Countless trillions of these little opal shells fell to the floor of ancient seas. They formed layers of gritty earth. This is the stuff we use as cleaning powder. The basic ingredients of opal are present, but the mineral is not arranged in fine layers to show the glowing colors of the rainbow.