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Rose Quartz
 Rose quartz -- an opaque to translucent macro-crystalline
quartz of pink to rose-red color -- is one of the most desirable varieties of
quartz because of its unique color and beauty. The composition of its color is
not completely understood. Formerly, it was attributed to a number of different
minor impurities, including titanium, iron, manganese, and even colloidal gold.
However, recent studies using micro-analytical methods have discovered that the
color of massive rose quartz is actually due to microscopic mineral fibers in
the quartz. X-ray diffraction tests on these microscopic fibers yielded
patterns similar to the mineral dumortierite but slightly different, suggesting
the possibility of a totally new and as yet unknown fibrous mineral causing the
color in massive rose quartz. The rare transparent crystals of rose quartz owe
their coloration to aluminum and phosphorous impurities; their pink color is
photosensitive and can fade in sunlight.
Rose quartz, which is considered a
semi-precious gemstone, is used as an ornamental stone, made into cabochons,
and carved into spheres, pyramids,
beads, hearts, and other figures. It's also a popular stone for
tumbling. Although it is usually too cloudy to be used as a cut gemstone, a few
exceptional pieces are found with enough clarity and color to make fine gems. Brazil is the only source of true, well-formed crystals of
rose quartz. All rose quartz was believed to be only massive, found primarily
in the cores of pegmatites. This lack of crystals is somewhat of a curiosity
because quartz crystallizes into well formed crystals in all its other
macroscopic varieties, such as citrine, amethyst, and smoky quartz. So amazing are the rose quartz crystals that
the first ones discovered were dismissed as fakes by mineralogists from around
the world!
 Rose quartz is considered to be a symbol of love and beauty. Metaphysically, it helps to open the heart chakra and balance the
emotions, thus giving inner peace and harmony. It is said to be the stone of
unconditional love, opening the heart to all forms of love: self-love, family
love, platonic love, and romantic love. Rose quartz also is used as a
protective stone for pregnant or birthing mothers. Physically, rose quartz is
used in crystal healing to treat the heart, the circulatory system,
fertility, kidney disease, migraines, sexual dysfunction, depression,
addictions, spleen problems, and fibromyalgia. It is also believed to help
control weight loss, slow signs of aging, and reduce wrinkles, giving a clear
soft complexion. The astrological signs of rose quartz are Taurus and Libra.
Rose Quartz: SiO2, Silicon Dioxide
Hardness: 7
Luster: vitreous
Class: tectosilicate
Color: pale-pink to rose-red
Transparency: opaque to translucent, rarely transparent
Fracture: conchoidal
Crystal system: Hexagonal-Rhombohedral; 32 (trigonal-trapezohedral)
Crystal habit: Usually massive with occasional contact crystal faces, occurs rarely as small horizontally striated hexagonal prisms terminated by a combination of positive and negative rhombohedrons forming six sided pyramids.
Specific gravity: 2.65
Index of refraction: 1.54-1.55
Cleavage: none
Streak: white
How Geodes are Formed
 Geodes are the mysterious treasure-boxes of the geological
world. Undistinguished lumpy balls of rock from the outside, they often reveal
crystal-lined interiors when cut or broken open. The crystals are most often
clear quartz, although they are sometimes amethyst or calcite. Rarely, crystals of pyrite, sphalerite, and other minerals may also be found.
Geodes may be less than an inch in diameter, though some, like the Brazilian amethyst cathedrals, can be several feet across. Some
geodes, commonly referred to as duds, are empty; others are solid crystal, or
nearly so, these are called nodules. There's no way of telling what you will
find in a particular geode from looking at the outside, although nodules are
noticeably heavier than hollow geodes.
Not all geologists agree on the exact
processes involved in the formation of geodes. Given that geodes form in both volcanic and sedimentary rocks under very different
conditions, the subject is a complex one. The most common theory is that geodes
form inside already existing hollows within the rock. In the case of volcanic
rock these hollows are the result of gas bubbles in the molten flow. Cavities
in sedimentary rock may be the result of concretions of an expansion in the
rock due to internal fluid pressure, or of the dissolving of earlier material
by groundwater – or any combination of these causes.
 Groundwater laden with silica and other
minerals fills these hollows. Over thousands of years minerals precipitate out
of the water, leaving a silica gel on the interior walls of the cavity that
hardens into rock as it dries. The first layer is usually chalcedony, a strong crypto-crystalline form of quartz. As
this process of mineral precipitation reoccurs, through leaching, layers begin
to form distinct, inwardly pointing crystals. Geodes that are empty missed
these later cycles. Multiple geodes are often found on the top layer of rock.
These, unfortunately, are usually the duds that were above groundwater.
How to Identify Rocks and Minerals
Field identification of rocks and minerals
can be an approximate, best-guess sort of business. If you have a good field
guide in hand, however, noting a few basics about a specimen will get you
started in the right direction.
Minerals
Because minerals
occur in a pure form, they are relatively easy to identify. Some of the
characteristics that can be used to make this determination are:
 Hardness: This is measured with the Mohs scratch test. Minerals range from very soft, like talc (Mohs 1), to exceedingly hard, like diamond, (Mohs 10). You can carry a Mohs Hardness Testing Kit with you into the field, or you can use a more informal method. Fingernails are about Mohs 2½, so if you can scratch your sample with your nail, it's Mohs 2 or less. A piece of glass or a knife blade is about Mohs 5½, and a steel file is Mohs 6 - 7.
- Color: Sometimes the color is diagnostic, as with the
vividly green mineral malachite. Other minerals may show a number of
different colors due to trace minerals or other conditions. Pure quartz crystals are clear as water, but a minute
amount of iron will tint them purple, while exposure to natural radiation will turn
them a deep, smoky brown.
- Fluorescence: Many minerals will glow vividly under
short- or long-wave light. The color a particular specimen fluoresces can help identify not only what it
is, but sometimes where it comes from (if you didn't find it yourself). To
make the test you'll need a UVP lamp (short-wave, long-wave, or combination), a guide
to fluorescent minerals, and a dark place. Not all specimens of a
particular mineral will fluoresce, however, so if you get no response, go
on to another test!
- Crystal Habit: Minerals are crystalline by nature. Although with some of them
this may be very hard to see, a hand lens or jeweler's loupe may be of assistance. If your specimen
shows a definite crystalline structure, this is a good clue to its identity.
There are six basic kinds of crystal structure, with a number of
variations. Fluorite is generally isometric, forming a cube. Quartz is hexagonal, or six-sided. The other crystal forms are tetragonal, orthorhombic, monoclinic, and triclinic -- your field guide will describe them in detail, along with their variations.
Rocks
Rocks are more difficult. When you set out
to identify them the first thing to know is that there are basic three kinds,
classified by how they were formed. These are Igneous, Sedimentary, and Metamorphic:
 Igneous rocks are cooled and hardened magma, a
molten material that comes from far below the Earth's surface. They tend to be harder than Mohs 5½ and to lack any sign of layering. If the magma hardens while still underground, the rock is called intrusive; if aboveground, as in a volcanic eruption, it's called extrusive. The intrusive (or plutonic) rocks tend to have an interlocking coarse-grained to medium grained texture, like granite. The extrusive (or volcanic) rocks may be very dense and fine-grained, like obsidian, or full of holes from gas bubbles, like pumice and basalt. Igneous rocks may contain small rounded crystals or little pieces of mica throughout the specimen.
 Sedimentary rocks are the result of the wearing away of older rocks by wind and water. The resulting debris is deposited in layers that in turn become cemented into new rock. Hardness varies from Mohs 1 up to about Mohs 7 and usually has a layered appearance. They get their name from the Latin word sedere, meaning "to settle." Fossils are common, as are ripple marks and mud cracks. Grain size can be anywhere from large pebbles in conglomerates and breccias down to very fine in chemical precipitates such as limestone. Dolomite, sandstone and limestone are all sedimentary rocks.
 Metamorphic rocks are transformed from older rocks by heat and pressure. They start out as igneous, sedimentary, or other metamorphic rocks, and show a wider range of characteristics than do the other two rock types. Still, there are a few indications that you can use. Mineral in the rock will be larger, better formed and better aligned than the parent rock. Layers that appear bent or crumpled are a good clue to a metamorphic origin. If your specimen doesn't appear to be either sedimentary or igneous, you may well start searching for it under the metamorphic heading! Marble, serpentine, and slate are all good examples of metamorphic rock.
Read more about the Identification of Rocks and Minerals on our website.
Geology Word Puzzler
What do you call a mineral that steals another mineral’s form, but replaces the previous rock’s composition with its own chemical compound?
A pseudomorph is a mineral compound resulting from a substitution process in which the appearance and dimensions remain constant, but the mineral which makes up the chief component of the compound is replaced by another. The name literally means false form. (definition from Wikipedia)
There are three kinds of pseudomorphs:
- A paramorph (also called allomorph) is a mineral changed on the molecular level only. It has the same chemical composition, but with a different structure. The mineral looks identical to the original unaltered form. This occurs in the aragonite to calcite change.
- An infiltration pseudomorph is when one mineral or other material is replaced by another. The original shape of the mineral remains unchanged, but color, hardness, and other properties change to those of the replacing mineral. This occurs in petrified wood when silica (either quartz or opal) replaces the wood.
- An incrustation pseudomorph results from a process by which a mineral is coated by another and the encased mineral dissolves. The encasing mineral remains intact, and retains the shape of the original mineral or material.
We'd love to hear from you! Have questions or comments about the website, or just want to tell us about your latest
rockhounding adventure? Email us at we_rock@mamasminerals.com!
Read about rose quartz, geodes, and identification of rocks and minerals in the Fall 2006 issue of RockZ NewZ
Read about fluorite, fluorescent minerals, and cleaning quartz in the Summer 2005 issue of RockZ NewZ.
Read about vanadinite, building fountains, and identifying meteorites in the Winter 2004 issue of RockZ NewZ.
Read about celestite, pearls, and how to choose the right rock tumbler in the Fall 2004 issue of RockZ NewZ.
Read about malachite, tumbling grits, and how to pan for gold in the Summer 2004 issue of RockZ NewZ.
Read about amethyst, fossil preparation, and field tools for the rockhound in the Spring 2004 issue of RockZ NewZ.
Read about galena, petrified wood, and collecting micrometeorites in the Winter 2003 issue of RockZ NewZ.
Read about iron pyrite, tumbling seaglass, and stony meteorites in the Summer 2003 issue of RockZ NewZ.
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