CHLORITE QUARTZ CLUSTER
A amazing Himalayan Chlorite Quartz Cluster. A piece of rock with beautiful Quartz Crystals with inclusions of rutile and chlorite above. This cluster is mounted on perspex for the cabinet, it is a collection worthy and interesting mineral specimen.
Dhading District, Nepal
6.7cm x 4cm x 4cm, 70g
General name for several minerals that are difficult to distinguish by ordinary methods Chlorite. These minerals are all apart of the Chlorite Group of minerals. The Chlorites are often, but not always considered a subset of the larger silicate group, The clays. There are several different minerals that are apart of the Chlorite group of minerals. The above formula is only a generalization of the more common members of this group.
Chlorites are generally green and crystallize in the monoclinic symmetry system. They all have a basal cleavage due to their stacked structure. However Chlorites also form large individual tabular to platy crystals that are unlike most of the other clay minerals.
Interesting is the formation of a Phantom inclusion inside a Quartz crystal. This happens when Chlorite coats a Quartz crystal the the Quartz crystal continues to grow. Many times the interior “crystal” is indistinct or ghostly and thus the name phantom. There is also a beautiful moss green formation which looks amazing under magnification. Chlorite needles are interesting and tend to grow in a star cluster form, used for thousands of years as a tattoo needle. For some reason the Quartz crystals tend to form more sharper points and slender bodies.
The local experts tell me that the Chlorite acts like an acid and eats away at the quartz whist forming. This is why some Chlorite formations look eroded.
Color is usually green but can also be white, yellow, red, lavender and black.
Luster is vitreous, dull or pearly.
Transparency: Crystals are translucent transparent.
Crystal System is monoclinic; 2/m.
Crystal Habits: Rarely in large individual barrel or tabular crystals with an hexagonal outline. Usually found as alteration products of iron-magnesium minerals and as inclusions in other minerals. Aggregates can be scaly, compact, platy and as crusts.
Cleavage is perfect in one direction, basal; not seen in massive specimens.
Fracture is lamellar.
Hardness is 2 – 3
Specific Gravity is variable from 2.6 – 3.4.
Streak is pal green to gray or brown.
Other Characteristics: Cleavage flakes are flexible but not elastic.
Include garnets, biotite, quartz, magnetite, talc, serpentine, danburite, topaz and calcite, among many others.
Notable Occurrences include Transvaal, South Africa; Zermatt, Switzerland; Guleman, Turkey; Lancaster Co., Pennsylvania, Brewster, New York; San Benito Co., California, USA and many other locallities world wide.
Best Field Indicators color, cleavage, associations and crystal habits.
Quartz Sample Images
Quartz is a fascinating common mineral, found in the Earth’s crust. If pure, quartz forms colourless, transparent hard crystals with a glass like luster. A significant component of many igneous, metamorphic and sedimentary rocks. Found in an abundant variety of formations and colors.
Polished Quartz was the most advanced technology thousands of years ago, used by the Assyrians. As a lens to focus light, could help start a fire for cooking. The Vikings could have used one of these to find the sun on a cloudy day. As a magnifying glass the ancients could see the stars too. Today it leads technology being the main component of transistors which make our computers work and solar panels.
The presence of trace elements gives an abundance of color range and crystal forms. Quartz is hard 7, light 2.65 and just adorable with an amazing shine when polished. No cleavage, characteristic conchoidal fracture and strongly piezoelectric and pyroelectric. Interestingly except in Twins where the opposites cancel each other out.
Chemistry: SiO2 , Silicon dioxide
Uses: silica for glass, electrical components, optical lenses, abrasives, gemstones, ornamental stone, specimens, building stone, etc.
Variety specimens include.
Amethyst is the purple gemstone variety.
Citrine is the yellow to orange gemstone variety. It is rare in nature and often created by heating Amethyst.
Milky Quartz is the cloudy white variety.
Rock crystal is clear quartz and used as a gemstone.
Rose quartz is a pink to reddish pink variety.
Smoky quartz is the brown to gray variety.
Clear quartz is the most common color then white or cloudy milky quartz. Purple (Amethyst), pink (Rose Quartz), gray or brown to black (Smoky Quartz) are also common.
Luster is glassy to vitreous as crystals, while cryptocrystalline forms are usually waxy to dull but can be vitreous.
Transparency: Crystals are transparent to translucent, cryptocrystalline forms can be translucent or opaque.
Crystal System is trigonal; 3 2.
Crystal Habits are again widely variable. A prominent habit is hexagonal prisms, terminated with a six sided pyramid. This is two rhombohedrons. Three of the six sides of the pyramid may dominate causing the pyramid to be or look three sided. Left and right handed crystals are possible and identifiable only if minor trigonal pyramidal faces are present. Druse forms (crystal lined rock with just the pyramids showing) are also common. Massive forms can be just about any type but common forms include botryoidal, globular, stalactitic, agate.
Cleavage is very weak in three directions (rhombohedral).
Fracture is conchoidal.
Hardness is 7, less in cryptocrystalline forms.
Specific Gravity is 2.65 or less if cryptocrystalline. (average)
Streak is white.
Other Characteristics: Striations on prism faces run perpendicular to C axis, piezoelectric (see tourmaline) and index of refraction is 1.55.
Associated Minerals are numerous and varied but here are some of the more classic associations of quartz. Amazonite a variety of microcline, tourmalines especially elbaite, wolframite. But wait there’s more pyrite, rutile, zeolites, fluorite, calcite, gold, muscovite, topaz, beryl, hematite and spodumene.
Notable Occurrences of amethyst are Brazil, Uraguay, Mexico, Russia, Thunder Bay area of Canada, and some locallities in the USA. For Smoky Quartz; Brazil, Colorado, Scotland, Swiss Alps among many others. Fine examples of Rock crystal come from Brazil, Arkansas, many localities in Africa. Fine Agates come from Brazil, Lake Superior, Montana, Mexico and Germany.
Best Field Indicators are first the fact that it is very common. Then crystal habit, hardness, striations, good conchoidal fracture and lack of good cleavage. Assume transparent clear crystals may be quartz.
Rutile; one of five forms of titanium found in nature. Titanium is three times stronger than steel and less than half the weight. Weighing only 42% as much as Steel, making it a stronger and lighter metal. It is chemically inert under normal conditions, enabling its use in medical implants such as pacemakers. This non corrosive metal is able to withstand temperature extremes up to 1800°C and has great strength. An outstanding high tech metal with amazing properties.
Hard 6 to 6.5, heavy, fragile and perfect cleavage. Opaque with metallic luster. Brown streak. Common accessory mineral in intrusive and metamorphic rock or in Quartz veins. Found mostly in sands as ore material for Titanium and rarely in a solid metal crystal.
Color is black or reddish brown in large thick crystals or golden yellow or rusty yellow as inclusions or in thin crystals.
Luster is adamantine to submetallic.
Transparency: Crystals are transparent in rather thin crystals otherwise opaque.
Crystal System is tetragonal; 4/m 2/m 2/m.
Cleavage is good in two directions forming prisms, poor in a third (basal).
Fracture is conchoidal to uneven.
Hardness is 6 – 6.5.
Specific Gravity is 4.2+ (slightly heavy).
Streak is brown.
Crystal Habits include eight sided prisms and blocky crystals terminated by a blunt four sided or complex pyramid. Composed of two, four sided prisms with one of the prisms being dominant. Crystals with some twins forming hexagonal or octahedral circles. A very common habit is thin acicular needles (especially as inclusions in other minerals) or as blades.
Elongated, prismatic crystals, often striated and slender. Commonly occur as inclusions in Quartz, known as “Maidens Hair” or criss – crossing at 60° Sagenite. The Yellow, Red, Brown, Black, Golden or Silver colors are amazing. Elbow and heart shaped (Geniculated) twins are common. Cyclic twin forming is comprised of six or eight twins arranged radially. A Rutile Star is a formation of crystals of Rutile in a six rayed orientation. Crystals grow off of a hematite crystal and the orientation is caused by its six rhombic faces.
Other Characteristics: Striations lengthwise on crystals, high refractive index (2.63) gives it a sparkle greater than diamond (2.42).
Associated Minerals are Quartz, Tourmaline, Barite, Hematite and other oxides and silicates.
Microscopic inclusions of Rutile in quartz, tourmaline, ruby, sapphire and other gemstones, produces light effects such as cat’s eye and Asterisms (stars). Rutilated quartz is produced at high temperatures and pressure, n(SiO2)-n(TiO2) in a stable state, as temperatures cool and pressure eases. The two separate with Rutile crystals trapped inside the quartz crystals.
Notable Occurrences include Minas Gerias, Brazil; Swiss Alps; Arkansas, USA and some African locallities.
Best Field Indicators are crystal habit, streak, hardness, color and high index of refraction (luster).