Mineralpedia Details for Calcite

Named for an important industrial use of the mineral after the Latin word calx, or calce, for “lime.” Calcite is extremely common and widespread, and it is an important rock forming mineral and is common in limestone, marble, chalk, as a cement, hydrothermal veins, igneous rocks, and caves. Calcite is highly variable in color and forms, but it is most easily recognized by its reactivity to hydrochloric acid and even weaker acids like vinegar, which it will effervesce strongly when in contact with. Calcite can fluoresce red, blue, yellow, and many other colors and shades under both long-wave and short-wave ultraviolet light. It is also phosphorescent, cathodoluminescent, thermoluminescent and occasionally triboluminescent. Another telling property of Calcite is its strong optical birefringence which causes a double refraction, and thus double image, which can be viewed by looking at objects through a clear calcite specimen.

Ref. Handbook of Mineralogy, Anthony et al (1995) and MSA at http://www.handbookofmineralogy.org/pdfs/calcite.pdf

Formula

CaCO₃ 

Crystal System

Trigonal 

Crystal Habit

Crystalline - Coarse, Stalactitic, Massive 

Cleavage

Perfect, Perfect, Perfect 

Luster

Vitreous (Glassy) 

Color

colorless, white, pink, yellow, brown 

Streak

white 

Class

Trigonal - Hexagonal Scalenohedral 

Fracture

Brittle - Conchoidal 

Hardness

3 

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Soft yellowish brown colored Calcite with crystals from 4 to 5 cm, one is doubly terminated. 

Large 4cm Calcite crystals showing striated faces with included Orpiment and external, prismatic, bright red Realgar crystals to 7mm. 

Glassy purplish pink Calcite rhombs to 5mm.

Clear Calcite crystal on Dolomite. 1cm.

An aestethic group of huge nearly 5cm translucent white Calcite crystals that are very well formed and take an interesting nailhead/modified rhombohedral form. Classic and highly sought locality for the Wisconsin collectors! Minor scuffing. Minor fluorescence to a light orange.

You've seen plenty of these on the market these days. It's a popular American locality which has produced countless beautiful groups of Fluorite, Calcite, Sphalerite and Barite. This specimen is nearly flawless, albeit, a partially cleaved matrix base, although you can expect that with any Elmwood piece. This crystal has the best amber orange color sought after in these pieces, the luster is great and the crystal edges are sharp. The large main crystal is 9cm long, You can see the twin plane in a few photos. With a little help, it displays marvelously.

Aesthetic specimen of orange, discoidal Calcite to over 1cm in nice clusters on Quartz. The original tag (prov. tab) shows it to be from the "Coronation Lode" of the Geevor mine.

Basic rhombs of Calcite with stepped edges and good luster. Crystals to 2cm. 

Snow white, beautifully stark cluster of Calcite rhombic crystals from 3mm to 25mm.

Groups of discoidal crystals once called "Poker-Chip" Calcite. The largest crystal ti 5cm across and all the larger crystals have grey bands. Sits and displays nicely.

Calcite 3.5cm across on matrix.

Orange-pink stained Calcite showing nice clusters of spear-shaped crystals from 2 - 10mm.

Honey yellow scalenohedral crystals to 2cm with curved edges.

Flat rhombic or discoidal crystals of Calcite to 1.5cm on Dolomite.

A nice group of iron-stained dog-tooth Calcite crystals to about 5-6mm in open geode-like vug.

Two nail-head light honey colored crystals one to 3cm the other to 2.5cm on Dolominte & Galena matrix with micro Chalcopyrite crystals.

Scalenohedral crystals with red hematitic tips. 

Large rhombic color zoned Calcite crystals from 2-3.5cm. 

Group of divergent columnar Calcite crystals with cavernous centers filled with tiny rhombic crystals as is the outer "prism" faces. This occurence is noted in the Dal'negorsk book by the Mineralogic Almanac volume 4, 2001 titled "DALNEGORSK". A photo of this same occurence and habit is shown on page 47, in which it is described as "case-like".

Calcite with crystals up to 6mm.

A nice 3cm yellowish gold crystal to 3cm across.

Two generations of Calcite with scalenohedral (1cm) crystals topped with a short prismatic nail-head (3mmx6mm) Calcite crystal. 

Two Calcite crystals perched nicely on top of mixed adularia, hematite, copper matrix. The two crystals are coated with an orange crust giving it a nice coloration. Each crystal is about 1.3cm.

Magenta rhombic crystals from 1-5mm. Brilliant color and beautiful specimen.

Water clear rhombic crystals mostly at 2-3mm, but also one large at 1.2cm. The crystals are on Marcasite as seen in the photos, which in turn are on Galena.

Calcite, especially this size, is rare in pegmatites. Most carbonates are associated with the primary phosphates. This specimen is an unusually large Calcite crystal perched nicely on Microcline. The specimen was photographed for figue 4-24 in London's "Pegmatites" book. See prov. tab for London't label.

A good dogtooth habit Calcite from this important mercury locality. A hint of things to come.

Large cabinet specimen full of 1 to 3cm scalenohedral Calcite crystals with a light coating of Marcasite. Really a nice showy specimen. Very little damage with only one cleaved crystal.