Name/Title
RhodochrositeEntry/Object ID
2004.1.159Description
Chemical Composition: MnCO3 / SiO2
Crystal System: Tetragonal System
Description: Common Name: Rhodochrosite / Quartz
Chemistry: MnCO3, Manganese Carbonate / SiO2 , Silicon dioxide
Group: Carbonates / Silicates
Location: Peru
Description: Large specimen with small, uniform, dull pink crystals and a druzy translucent quartz covering on a gray to light pink matrix, with some mixed in the crystals intermitently.
PHYSICAL CHARACTERISTICS OF RHODOCHROSITE:
Color is red to pink, sometimes almost white, yellow and brown.
Luster is vitreous to resinous.
Transparency: Crystals are transparent to translucent.
Crystal System is trigonal; bar 3 2/m.
Crystal Habits include the rhombohedrons and scalahedrons with rounded or curved faces that can obscure the crystal shape. Some crystals can be flattened to a bladed habit and these are sometimes aggregated into rosettes or minute crystals into spherules. Also botryoidal, globular, stalactitic, layered, nodular, vein-filling and granular. Twinning is somewhat common forming penetration twins and contact twins similar to calcite's twins.
Cleavage is perfect in three directions forming rhombohedrons.
Fracture is uneven.
Hardness is 3.5 - 4.
Specific Gravity is approximately 3.5 (above average)
Streak is white.
Other Characteristics: Pink and white banding in massive forms, non-fluorescence and specimens effervesce easily with dilute acids.
Associated Minerals include calcite, ankerite, alabandite, rhodonite, bementite, spessartine, fluorite, manganite, quartz and many metal sulfides.
Best Field Indicators are color, crystal habit, reaction to acid, non-fluorescence and perfect cleavage.
PHYSICAL CHARACTERISTICS OF QUARTZ:
Color is as variable as the spectrum, but clear quartz is by far the most common color followed by white or cloudy (milky quartz). Purple (Amethyst), pink (Rose Quartz), gray or brown to black (Smoky Quartz) are also common. Cryptocrystalline varieties can be multicolored.
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 but the most common habit is hexagonal prisms terminated with a six sided pyramid (actually 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, crusts of agate such as lining the interior of a geode and many many more.
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 (although any list of associated minerals of quartz is only a partial list): amazonite a variety of microcline, tourmalines especially elbaite, wolframite, pyrite, rutile, zeolites, fluorite, calcite, gold, muscovite, topaz, beryl, hematite and spodumene.
Best Field Indicators are first the fact that it is very common (always assume transparent clear crystals may be quartz), crystal habit, hardness, striations, good conchoidal fracture and lack of good cleavage.
Fracture: uneven
Hardness: 4 Flourite
Luster: Vitreous
Occurrence: Rhodochrosite occurs as a hydrothermal vein mineral along with other manganese minerals in low temperature ore deposits as in the silver mines of Romania where it was first found.
Colorado officially named rhodochrosite as its state mineral in 2002 based on a proposal by a local high school (Platte Canyon High School in Bailey,Colorado). The reason for this lies in the fact that while the mineral is found worldwide, large red crystals are found only in a few places on earth, and some of the best specimens have been found in the Sweet Home Mine near Alma, Colorado.
Quartz is an essential constituent of granite and other felsic igneous rocks. It is very common in sedimentary rocks such as sandstone and shale and is also present in variable amounts as an accessory mineral in most carbonate rocks. It is also a common constituent of schist, gneiss, quartzite and other metamorphic rocks. Because of its resistance to weathering it is very common in stream sediments and in residual soils.
Quartz occurs in hydrothermal veins as gangue along with ore minerals. Large crystals of quartz are found in pegmatites. Well-formed crystals may reach several meters in length and weigh hundreds of kilograms.
Rock Type: Sedimentary
Specific Gravity: 3.5
Streak: white
Variety: Individual crystals are found in well shaped rhombohedrons and more rarely scalahedrons. In a massive form its pink and white bands are extremely attractive and are often used in semi-precious jewelry. Rhodochrosite is often carved into figurines and tubular stalactitic forms are sliced into circles with concentric bands that are truly unique in the mineral kingdom. Fine crystals are sometimes cut into gemstones, but rhodochrosite's softness and brittleness limit it as a gemstone for everyday use.
Identification of rhodochrosite is fairly easy despite a few similarly colored minerals such as rhodonite. Rhodonite is harder and has different cleavage; but perhaps the best distinguishing factor is its lack of reaction to acids. Rhodochrosite will easily with show some reaction to cold acids which demonstrates its carbonate chemistry. Basically, any rose-pink carbonate is considered rhodochrosite; however some calcites with a small amount of manganese impurities can be pink in color. The manganese replaces some of the calciums in calcite but a complete series between calcite and rhodochrosite is not established. Differentiating pink calcite from rhodochrosite may require a fluorescence test as rhodochrosite is distinctly non-fluorescent and manganese is a fluorescent activator in calcite.
Quartz is the second most abundant mineral in the Earth's continental crust, after feldspar. It is made up of a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall formula SiO2.Collection
RAGM Mineral CollectionAcquisition
Accession
2004.1Source or Donor
Suomynona Mineral CollectionAcquisition Method
DonationDimensions
Width
4-3/4 inDepth
5 inLength
8-1/2 inWeight
8.26 ozLocation
Location
Display Case
DS-8Room
Delmar Smith HallBuilding
Crater Rock MuseumCategory
PermanentMoved By
Curtis GardnerDate
May 25, 2023Notes
Added current locationLocation
* Untyped Location
Needs Updated Location - 2022Category
PermanentMoved By
Scott LonganDate
September 26, 2009Location
Container
LeftDrawer
3rd shelfShelf
LeftCabinet
Case #39Wall
West wallRoom
Delmar Smith HallBuilding
Crater Rock MuseumCategory
Permanent