Garnet, found in the Wissahickon Gorge, serves as a substitute for more expensive red gemstones such as rubies.
The Wissahickon Gorge is in Philadelphia, Pennsylvania, and is a geological site populous with common rocks and minerals. Though there is not an abundance of gems in the area which would be suitable for jewelry or collections, it has many minerals and crystals which may double for gemstones, are sometimes used as mineral specimens or for industrial purposes. Minerals and crystals are categorized and rated based on their transparency, usually the more transparent the better; cleavage, which refers to how smooth it is when split; and color. Does this Spark an idea?
Biotite
Biotite mica ranges from transparent to translucent and is colored black, dark green or dark brown. Biotite is recognized due to its cleavage because it separates into thin, flexible sheets which are nearly perfect. As a commercial product it serves as a surface treatment in construction material, and geologists use it to date rocks.
Chlorite
Chlorite typically has a strong green color and forms microscopic crystals which are flaky. It most often appears within or on the outer coating of quartz, topaz, danburite or calcite. Chlorite crystals are translucent or transparent, and though it is usually green other color formations include white, red, lavender, yellow and black.
Garnet
Garnet is a crystal which forms under high temperature and pressure, and due to its color and transparency is often a candidate for being a gemstone except that it is relatively abundant and therefore cheap to purchase. Garnets come in multiple different types, the most common being alamandine, andradite, grossular, pyrope, spessartine and uvarovite. In these common varieties is a wide color spectrum including reddish brown, brown, black, green, colorless, orange, dark red, ruby red, orange and pink, though most garnet crystals are red. All garnets are alike in that they are highly transparent and brightly colored.
Kyanite
Kyanite is an aluminum silicate used to manufacture spark plugs. It is mostly sapphire-blue, though it can also be white, gray or green. A marked characteristic of kyanite is that it forms in long, splintery prismatic crystals which makes it popular as a mineral specimen. Kyanite crystals range from transparent to translucent and appear in metamorphic rocks and quartz veins.
Muscovite
Muscovite is common in a range of different rocks and serves as a heat and electrical insulator for industrial products and purposes. Muscovite crystals can be transparent or translucent and are colored white, silver, yellow, green or brown. The crystals cleave off in thin sheets or flakes which are flexible, elastic and uneven.
Sillimanite
Sillimanite is rarely used as a gemstone or mineral specimen but is used in industries such as cement making, glass making and iron foundries. Sillimanite is transparent or translucent and white, gray, brown or yellow. The crystals are needle-like and cleave lengthwise.
Staurolite
Staurolite is a mineral distinguished by its crystals which form cross shapes or sometimes a six-rayed star. Staurolite crystals range from translucent to opaque and are colored reddish-brown, brown or black. It has no industrial uses and serves primarily as a mineral specimen.
Tourmaline
Tourmaline is a group of different, albeit closely related, minerals. People use it as a specimen in collections, carve it into figurines or craft it as a gemstone. Colors of tourmaline are highly variable, the most common being shades of brown, red, pink, green, orange, blue and yellow. Its crystals are translucent or transparent and are typically elongated prisms.
Tags: crystals which, transparent translucent, mineral specimen, brown black, common being
