is dense volcanic glass usually black in color. Inclusions and bubbles add color
and patterns to some types of obsidian. It is often formed in rhyolite lava
flows when the lava cools quickly enough to prevent crystal formation. Glass
has no regular structure and fractures in round smooth sections. These can form
an extremely sharp edge and obsidian was used by many cultures for knives and
arrowheads. Today obsidian bladesare used in heart
surgery, and have a cutting edge much sharper than surgical steel scalpels.
Jasperis produced from a mine in
Madagascar. It is an unusual and beautiful stone with extraordinary markings
in a variety of colors. Primarily pure silica which has been converted from
rhyolite. It falls into the orbicular jasper category, since traditionally
rhyolite with enough silica to take a polish has been labeled jasper. It may
also be considered an agate as it is translucent while jasper is opaque. The
label ďoceanĒ comes from the location where it was discovered along the coast
and the patterns in the rock are suggestive of ocean waves.
is a cryptocrystalline form of quartz. Bands are usually white, tan and brown
but can be a wide variety of colors. Sardonyx has red bands of color. Black
Onyx is less common than banded Onyx. Used for cabochons, beads and cameos.
Onyx has been used by a variety of Ancient cultures and civilizations.
Opal is a mineraloid
gel which may occur in the fissures of almost any kind of rock. The water content
is usually between three and ten percent but can be more. Opalís distinguishing
characteristic is itís fire or beautiful play of sparkling color unlike and
other stone. Opal can be clear, white, gray, red, orange, yellow, green, blue,
pink, olive, brown, and black. Red fire against black is the most rare and white
and green the most common. Opal is Australia's national gemstone. Some fossils
can be opalized.
Opalite is a type of opal without any fire called potch. Natural opalite often has dendritic
inclusions and is sometimes called moss opalite. The name moss opalite
may come from the moss like appearance of the dendrites or because opalite is
often associated with moss agate and plume agate. A dendrite is a branching
treelike figure produced by a foreign mineral. Opalite can be a variety of colors
from yellow, green, brown, white, tan, and peach.
Dinosaur Bone is the mineralized remains of dinosaur bone. As with other fossils the
original animal bone, shell or plant has been replaced by minerals or become
petrified. Dinosaur bone can come in a variety of colors most commonly
brown, dark red and grey although it can be yellow or orange.
is a rare type of petrified wood from Western Australia.
It comes from trees which grew 70 million years ago in the Cretaceous period.
Peanut wood refers to the appearance of the peanut shaped light color markings
against the blackish background of this petrified wood. Peanut wood was
created from wood washed into the ocean and infested by small marine clams.
The wood sank to the ocean floor, and the bore holes filled with sediment, that
later petrified. This unique process created a uniquely beautiful petrified
wood. Peanut wood has beautiful glossy shine when polished, and the lighter
beige colored markings are striking against the black background.
was discovered by Sid Pieters in 1962 in Namibia, Africa. Currently China and
Africa are the only known sources of Pietersite. Pietersite has brecciated,
fibrous bands of blue, gold and red tiger eye type fibers in quartz. The fibers
in Pietersite were folded, fractured and split, later reformed and naturally
cemented together with quartz by geological processes. Pietersite has the chatoyancy
of tiger eye with a chaotic pattern of colors.