Composition: Aluminum Oxide
Class: Oxides and Hydroxides
Crystal System: trigonal; bar 3 2/m
Specific Gravity: 3.99 - 4.0
Refractive Index: 1.757 - 1.779
Luster: vitreous to adamantine
Color: Most any color some stones show zoning
Cleavage: is absent, although there is parting which occurs in three directions
Transparency: Crystals are transparent to translucent
Associated Minerals: calcite, feldspars, garnets, micas and zoisite
Advances in sapphire heat treatment over the past two decades has opened
the doors to competition. It is an established fact that 90 percent of
all gem grade sapphire is heat-treated. Montana sapphire boasts a rainbow
of colors when properly treated. It is also renowned for its high refractive
index when properly cut and its ability to retain brilliance under a variety
of lighting conditions.
This process improves the sapphires, both in color and clarity. The heating
process does not use artificial coloring of any type, it simply causes
a property change in the stone that dissolves an element called rutile,
eliminating the cloudiness often seen in sapphires. The difference between
natural and heated stones is dramatic. Some stones are left in their natural state, particularly if they are gem quality. Only about 3-5% of Montana
Sapphires are gem quality as found.
An additional consideration when deciding whether to heat or not is the
color of the stone. Occasionally a stone is such a spectacular color,
that one has to decide whether or not to risk the possible color change
that may occur as a result of heating. There is no way to know for sure
what the end result will be, and sometimes the decision is made to leave
the stone in its natural state in order to retain the color.
Of the four Montana sapphire regions, only Rock Creek (just outside Philipsburg) Is known for its variety of distinctly crisp and sharp colors. As tastes
have shifted to more brilliant gem jewelry, Rock Creek sapphires have
come into their own. Particularly with the advent of readily available
Rock Creek sapphires are able to fill a niche worldwide. Colors range
from the classic "cornflower blue" to "red-orange" and "mint green." The
colorful variety of sapphires found and finished here have a character
and beauty all their own.
Montana is home to some of the largest Sapphire deposits in the world. Known as the "Native American Sapphire" Montana Sapphires are available in every imaginable color of the rainbow. Montana Sapphires are considered "Fancy" Sapphires, ( colors other than, but also including Blue ). Many experts rate Montana Sapphires as "The Finest Sapphires in the World!
FACTS & HISTORY:
One of the most popular attractions of the Philipsburg area is the sapphire
mining offered to the public. It is pretty unusual that people are able
to dig through gravel in search of rare, fine gems, but that is just what
is offered in Philipsburg. Year round, sapphire gravel is available for washing, and then if you
please, you can watch the sapphires get heat treated and prepared for
jewelry. There are several places in Philipsburg where you can find these
precious gems. The Sapphire Gallery and Gem Mountain mine located 22 miles from Philipsburg heat treat and cut these wonderfull stones.
Other Montana sapphire localities are located on the Missouri River
about 15 miles NE of Helena. If you look at a Highway map you will see
Canyon Ferry Dam east of Helena, and just to the west of it is Hauser
Lake. Spokane Bar is on the south side, west of the Dam and Eldorado Bar
is NW of that on the north side of the lake/river.
Links to digging sites: