Mineralogy

Mineralogy is the science of minerals. Minerals are single natural solid substances containing crystals. They may look like rocks, but minerals are more pure and singular. There are many minerals, about 2,500. Some are gems. If you collect minerals, you may want to know what there names are. You have to study their properties, or describe them. Then match up the properties with the names on the identification chart on this page.

Color

   The very first property you notice is color. Some minerals have certain colors. Rose quartz is usually pink. Halite is usually white. Citrine is usually golden or yellow.

    But some minerals can be more than one color. Hematite can be reddish-brown or black. More than one mineral can be the same. Diamond, fluorite, turquoise, and aquamarine can all be blue. So do not just use color for identification.

Luster

   Different minerals shine or appear in a different way. The Gem Hunter's Handbook says: "A piece of glass, a book cover, a shirt, and a rug can all be red, but each has a different appearance, ranging from very shiny to very rough and dull." It is the same way with minerals. The appearance and shininess of a mineral is its luster. A metallic luster (as with copper) looks like a coin or aluminum foil. A mineral that does not shine is called dull, nonmetallic, or earthy. A glassy mineral (such as quartz) is vitreous. If it is very brilliant, hard, and shiny (like a gem diamond), it is adamantine. Minerals that glimmer like pearls are pearly. Waxy minerals look like pieces of wax.

Opacity

    Another easy-to-see property is opacity, which tells how uneasily light passes through a mineral. You cannot see through a hematite because it is opaque [oh-'payk]. Light is either reflected or absorbed by opaque objects. Some light passes through translucent materials and when it passes through, some may be scattered. Quartz is sometimes translucent. You can see clearly through transparent materials.

Streak (True Color)

   Earlier said, minerals can be more than one color. But one mineral has one true color. Other chemicals added make varieties of color. You can find the true color by rubbing it on a streak plate or ceramic tile plate. Part of the mineral gets crushed and is let behind in a streak. Some minerals, especially diamond, are too hard to leave a streak.

        Hematite's streak is reddish brown (even if the hematite is black). Halite's and calcite's streaks are white. Streak, or true color, is a good way to identify minerals (better that just plain-old color).

Hardness

   Some minerals are harder than others. The durability of minerals, hardness, tells how uneasily a mineral can be scratched. Hardness is measured on a scale of one to ten. One is the softest; ten is the hardest. To measure hardness, take a mineral with a known hardness, such as quartz (7), and scratch it on a mineral with an unknown hardness. If the unknown-hardness mineral gets scratched, its hardness is less than 7. To specify that use other minerals and test the hardness with them. The hardness might prove to be a hardness of three (H=3).

        These minerals are not very common, so when testing hardness, you can use common, convenient substitutes. Fingernails and pencil lead has a hardness of about 2. Coins have about H=3. The iron inside a magnet has about H=4-4.5. Knives, glass, and obsidian has H=5-5.5 (hardness of five to five and a half). Nails and steel files have H=6.5. (When you identify hardness of minerals, you can add them to your hardness scale.)

Crystal Shape

   The shape of crystals also is an important property. Quartz has hexagonal crystals. Halite, calcite, and diamond have cubic crystals. The crystals in graphite (a major component of pencil lead) have layers. There are seven crystal shapes: cubic (cube), tetragonal (rectangular prism), hexagonal (hexagonal prism), rhombohedral (rhombus prism), orthorhombic, monoclinic, and triclinic (also rhombus prisms).

NOTE: Citrine to Milky Quartz are all forms of quartz (silicon dioxide Si-O2).

Glossary

adamantine ['ad-uh-mun-teen] adj. Hard and brilliant (in luster), like a diamond.

earthy ['ur-thee] adj, adv. earthily Having a non-shining luster; dull; nonmetallic.

hardness ['hahrd-nus] n, pl. hardnesses The unability to get scratched; durability. Derivation: -Ness means state of being; thus hardness means "hard state of being" or "state of being hard."

luster ['lus-tur] n. The appearance and shininess of an object such as a mineral.

metallic [muh-'tal-ik], also metallical adj, adv. metallically Having a luster similar to metal. Derivation: -Ic and -ical mean like; thus, metallic and metallical mean "like metal."

mineralogy [min-uh-'rah-luh-jee] n, pl. mineralogies The science of minerals -- natural solid substances with crystals. Derivation: -Logy means study; thus, mineralogy means "mineral study."

opacity [oh-'pas-it-ee] n, pl. opacities Unability to transmit light.

pearly ['pur-lee] adj. Glimmering in a way resembling pearls. Derivation: -Ly means like; thus, pearly means "like pearls."

streak ['streek] n. The color of powder from a mineral that has rubbed on a streak plate; true color.

true color ['troo kuh-lur] n, pl. true colors The color a mineral in its pure form.

vitreous [vi-'tree-us] adj, adv. vitreously Resembling glass in brittleness or luster; glassy.

waxy ['waks-ee or 'wak-see] adj. Resembling wax. Derivation: -Y means having, like, or covered with; thus, waxy means "like wax."