Lapis Lazuli (or Lapis for short) is a rock and not a mineral because it is made up of various other minerals.  It is composed of a mixture of several minerals including mostly Lazurite, Pyrite, Calcite and Diopside, along with possible inclusions of Sodalite, Huaynite, Noselite, Mica, Augite or Hornblende in small amounts.  Lapis usually occurs in crystalline limestones as a result of contact metamorphism. 
The name Lapis Lazuli comes from a variety of words meaning "blue" (azure) or "heaven": the Latin "lazulum", stemming from the Arabic "lazaward", and the Persian "lazhward" constitute the Lazuli part.  The first part of the name, Lapis, is of Latin origin meaning simply "stone".  And this stone was named after its likeness to the heavens and of course because of its color -- a brilliant deep blue (due to the sulfur content in the Lazurite) which is usually speckled or veined with small flecks of yellow-gold color from its most common mixture with Pyrite (Fool's Gold) or white streaks from its mixture with Calcite or other minerals. 
Lapis Lazuli is a semi-precious stone valued for its deep blue color and durability.  Though too many white streaks of Calcite will lower the value of the stone.
This is a picture of the actual stone used in the electrolysis process:
 
General Information: 
Chemistry:  (Na, Ca)8 Al6 Si6 (O,S)24 [(SO4),Cl2,(OH)2], Sodium  
Calcium Aluminum Silicate Sulfur Sulfate (with usual inclusions of Pyrite and Calcite). 
Class:  Silicates 
Subclass:  Tectosilicates 
Group:  Both the Sodalite and Feldspathoid groups. 
Color:  Deep brilliant blue or violet-blue with golden flecks or veins, and occasionally white streaks. 
Luster:  Dull to greasy. Translucent to opaque. 
Crystal System:  Isometric; bar 4 3/m 
Crystal Habit:  Massive as a rock (Lapis Lazuli) forming mineral, but dodecahedral crystals have been found of Lazurite. 
Cleavage:  Poor. In six directions, but rarely seen. 
Fracture:  Uneven. 
Hardness:  5.0 - 5.5 
Specific Gravity:  2.3 - 2.4 (somewhat below average, but shows higher with increased Pyrite content). 
Long ago, Lapis was used to make the pigment called Ultramarine, which literally meant "beyond the sea".  It was used by medieval artists for the blue cloak of the Virgin Mary.  Due to its rarity and expense, today that color pigment is usually now synthetically made. 
Metaphysical Properties: 
Astrological Sign(s): Sagittarius, Aquarius 
Chakra(s): Brow and Crown 
Opens the Third Eye. 
Awakens the intuition. 
Enhances insight and awareness. 
Brings knowledge and wisdom. 
Increases vibrational level. 
Connects to Spirit. 
Helps in meditations and dream work. 
Promote peace. 
Harmonizes and balances. 
Protective. 
Blocks psychic attack. 
*Gives physical aid in treating: Fevers. Headaches and migraines.  Alleviates pain. Depression and melancholy. Anxiety. Insomnia. Vision and hearing problems.  Disorders of the throat, lungs and immune system.  
*NOTE: Stone therapy should NOT take the place of medical evaluation and procedures, and should be used merely to enhance one's health and well-being. 
Lapis Lazuli is my "Awareness" stone.  Known for imparting ancient knowledge and (just as important) the wisdom on how to use that knowledge, Lapis is very helpful in bringing you into that state of awareness where you can better connect with your Higher Self or communicate with your Spirit Guides.  Rich and highly stimulating, it's easy to quickly feel the intense and royal powers of the stone lift you to new heights of thought, consciousness and awareness. 
Feeling that the stone was the best of the best when it came to spiritual stones, the "Sleeping Prophet", Edgar Cayce, recommending carrying a piece of Lapis Lazuli with you at all times wherever you go.  I used to.  And I think it's time I go back to doing just that. 
 
Meaning and Uses of Lapis Lazuli
Lapis Lazuli is one of the most sought after stones in use since man's history began. Its deep, celestial blue remains the symbol of royalty and honor, gods and power, spirit and vision. It is a universal symbol of wisdom and truth.
In ancient times Lapis Lazuli was most highly regarded because of its beautiful color and the valuable ultramarine dye derived from it. Its name comes from the Latin lapis, "stone," and the Persian lazhuward, "blue." It is rock formed by multiple minerals, mostly Lazurite, Sodalite, Calcite and Pyrite, and is a rich medium to royal blue with gold flecks (pyrites). Lower-grade Lapis is lighter blue with more white than gold flecks, and is sometimes called denim Lapis.
Lapis Lazuli was among the most highly prized tribute paid to Egypt, obtained from the oldest mines in the world, worked from around 4000 B.C. and still in use today. Referenced in the Old Testament as sapphire (unknown in that part of the ancient world), Lapis Lazuli is most likely the fifth stone in the original breastplate of the High Priest, as well as those of later times.
The golden sarcophagus of King Tutankhamen was richly inlaid with Lapis, as were other burial ornaments of Egyptian kings and queens. It was used extensively in scarabs, pendants and other jewelry, and ground into powder for dyes, eye shadow and medicinal elixirs. In the dry, barren land of the Egyptians, this deep cobalt blue color was a spiritual contrast to their arid desert hues. The gold flecks were like stars in their night-time sky and by meditating on these colors they felt supernatural forces would transform their lives. The garments of priests and royalty were dyed with Lapis to indicate their status as gods themselves.
In ancient Persia and pre-Columbian America, Lapis Lazuli was a symbol of the starry night, and a favorite stone of the Islamic Orient for protection from the evil eye. Lapis was much used in Greek and Roman times as an ornamental stone, and in medieval Europe, Lapis Lazuli, resembling the blue of the heavens, was believed to counteract the wiles of the spirits of darkness and procure the aid and favor of the spirits of light and wisdom. Ground and processed into powder, it produced the intense, but expensive, ultramarine color favored by the painter, Michelangelo. Buddhists recommended Lapis as a stone to bring inner peace and freedom from negative thought, and during the Renaissance, Catherine the Great adorned an entire room in her palace with Lapis Lazuli walls, fireplaces, doors and mirror frames.
Lapis Lazuli Purposes
Lapis is an excellent stone for executives, journalists, and psychologists, stimulating wisdom and good judgment in the practical world. It aids intellectual analysis in archeologists and historians, problem solving for lawyers, and creates new ideas for inventors and writers.
Lapis Lazuli is a powerful crystal for activating the higher mind and enhancing intellectual ability. It stimulates the desire for knowledge, truth and understanding, and aids the process of learning. It is excellent for enhancing memory.  
A stone of truth, Lapis encourages honesty of the spirit, and in the spoken and written word. Wear it for all forms of deep communication. It is also a stone of friendship and brings harmony in relationships. A Lapis grid brings calm and loving communication for a home with temperamental teenagers, or children with Asperger's syndrome, autism, or attention-deficit disorder.
For fame in a creative or public performance-related area, wear or carry Lapis Lazuli to auditions. In the workplace, it attracts promotion, success and lasting recognition in your field
Lapis Lazuli Physical Healing Energy
Lapis Lazuli is beneficial to the throat, larynx, and vocal chords, and helps regulate the endocrine and thyroid glands It overcomes hearing loss and other problems with ear and nasal passages.
Lapis Lazuli enhances circulation and improves cardiac rhythm. It reduces vertigo and lowers blood pressure, and is thought to alleviate insomnia.
Relieve oozing or septic sties, and other eye infections, by