What is an Arkansas stone?
Arkansas stones, also known as “Arkan” or Arkansas whetstones, are natural oilstones quarried in the State of Arkansas, USA, and are named after their place of origin. These natural whetstones are crafted from novaculite, an extremely hard, white rock composed primarily of microcrystalline quartz. Featuring a porous structure ideal for retaining oil, they are widely used as premium oilstones.
What is novaculite?
Novaculite is an extremely hard, white sedimentary rock composed of microcrystalline quartz. Furthermore, it is recognized as a recrystallized variety of chert, consisting of more than 99% pure silica. The name originates from its primary formations in Arkansas, Oklahoma, and Texas, and is derived from the Latin word “novacula,” meaning “razor stone.” Novaculite is a rare and one of the finest abrasives for sharpening stones.
Geological Background Found within strata ranging from 250 to 900 feet thick, novaculite was formed during the Mississippian and Devonian periods (approximately 350 million years ago). The stone naturally resists erosion, forming the prominent ridges of the Ouachita Mountains. While minable novaculite exists in vast quantities, whetstone-grade novaculite is extensively found in the lower strata of Garland County and its surrounding areas. Individual sources also stretch from Little Rock in Pulaski County westward to Hatton in Polk County. Thanks to the massive volume of novaculite in these geological layers, it remains possible to continuously produce Arkansas grinding and sharpening stones to meet ongoing demand.
The History of Mining According to mining records, early settlers in this region began quarrying around Magnet Cove in Hot Spring County in the early 1800s. Novaculite mining in Arkansas started intermittently from 1885 to 1905, and production levels have remained steady since that era.
Long before Europeans discovered the uniquely sharp and exceptionally abrasive qualities of Arkansas stones, Native Americans living in the region gathered to quarry novaculite for crafting weapons and tools, such as arrowheads, knives, and axes. Intertribal trade records reveal that these stones were distributed and used as far as 160 to 1,600 kilometers away from the original deposits.
Color of Arkansas whetstones
What colors do Arkansas Novaculite stones come in? Black, dark indigo, gray, white, a mixture of colors, brown, pink, or red?
Throughout the history of Arkansas stone production, an idea emerged that seemed practical at the time: associating the color of the stone with its grade. For instance, people thought a certain color indicated a hard stone, while another meant it was soft. Back then, it was considered a reasonable approach.
Today, however, we know that each grade of stone actually exhibits a wide variety of colors. Yet, those outdated, incorrect grading classifications still resurface occasionally, causing consumer confusion and restricting manufacturers.
Arkansas stones can be found in any of the following colors: pink, gray, red, black, dark indigo, white, and brown (including purplish-red). It is also common to find a combination of several of these colors within a single, identical stone.
The color of the stone does not determine its hardness. While a highly trained eye may use color as one of many factors to identify a stone’s grade, it is only reliable when evaluated alongside other key characteristics, such as translucency, texture, luster, weight, and the specific quarry stratum from which it was mined. Relying solely on color for grading is simply not accurate.
The grading process begins right at the quarry, where the composition is meticulously examined for its mineralogical properties. Novaculite has a distinct appearance where it fractures, known as a conchoidal fracture, which resembles a shell (imagine the wavy texture on the surface of a scallop shell). The surface is smooth; lower/softer grades have a dull luster, while higher/harder grades feature a glossy, almost glassy appearance. As a sedimentary rock, the deposits are interbedded with various types of shale, according to the Arkansas Geological Commission. For more comprehensive details regarding stone grades, please refer to our Stone Grades page.
・Stone Grade
1.What are the grit sizes for each grade of Arkansas stones?
Arkansas stones are classified by their specific gravity (relative density) rather than grain size. Even when a stone is categorized as a “Soft Arkansas” or a “True Hard Arkansas,” the quartz grains that form the novaculite are inherently the same size, measuring approximately 3 to 5 microns. A specific gravity test is utilized to measure the density of these stones—essentially, how closely packed the bonded grains are. Therefore, a firm “Hard Arkansas” stone contains a higher concentration of grains within the same volume than a “Soft Arkansas” stone.
Because the grain size of novaculite remains virtually constant, comparing it directly to the grit sizes of synthetic whetstones is extremely difficult. Furthermore, standard measurements for synthetic grits vary significantly across different countries. According to the grit standards used in the United States, pure novaculite is most closely equivalent to a range of #600 to #1200.
Our stone grades are distinguished solely by their specific gravity, classified as follows:
Soft Arkansas： Specific Gravity 2.25-2.30
Hard Select Arkansas： Specific Gravity 2.30-2.45
True Hard Arkansas： Specific Gravity 2.50 or higher
Black Hard Arkansas： Specific Gravity 2.50 or higher
Translucent Hard Arkansas： Specific Gravity 2.50 or higher
2.What causes the colors in novaculite, and do they affect the honing process?
To the best of our knowledge, the colors within the stone do not interfere with the honing process, nor do they create gaps or inconsistencies in the stone’s grade. During 350 million years of sedimentation and subsequent geological events, various minerals dispersed throughout the rock, causing these natural color variations. For example, the rusty red hues often found in True Hard Arkansas stones are primarily caused by traces of manganese. Users should rest assured that the color of the stone is not a definitive factor in classifying novaculite.
Novaculite is composed of 99.898% pure silica, containing only minute traces of other mineral elements, which do not impact its performance:
● Types of Arkansas Stones
Soft Arkansas (Medium)
The Soft Arkansas stone is the most popular grade of novaculite. It is a versatile, all-purpose whetstone primarily used by woodcarvers, outdoor sportsmen, butchers, commercial knife sharpeners, and home cooks. This grade is ideal for users looking to achieve a sharp, polished edge on knives and tools in the shortest amount of time. Soft Arkansas stones typically feature colors ranging from white, mixed gray and black, to combinations of pink and gray.
Hard Select Arkansas (Fine)
The Hard Select Arkansas stone is designed for customers who require a more refined, precise, and razor-sharp edge on their knives and tools. Although it is frequently referred to as the “White Arkansas,” this stone also often exhibits a variety of natural color patterns. It is highly popular among woodworkers and across various manufacturing industries. (Note: Raw mineral photos are unavailable for the Hard Select grade.)
True Hard Arkansas (Ultra-Fine)
The True Hard Arkansas stone stands as one of the finest abrasives available today. It is chosen primarily by professionals who demand an exceptional, top-tier polished finish. Often referred to as the “Multi-Colored Translucent Stone,” it features both translucent and semi-transparent qualities, with natural blends of black, red, white, and gray frequently coexisting within a single stone.
Black Hard Arkansas (Ultra-Fine)
Based on precise technical grading via specific gravity testing, the Black Hard Arkansas falls within the same premium density classification as the True Hard Arkansas. The further distinction between “Black Hard” and “Translucent Hard” within this top-tier category is simply a matter of user preference. Black Hard Arkansas stones are characterized by a solid black or deep indigo color.
Translucent Hard Arkansas (Ultra-Fine)
Just like the Black Hard, the Translucent Hard Arkansas is classified within the True Hard Arkansas category according to its specific gravity. Distinguishing it from the Black Hard is entirely a reflection of customer preference. Translucent Hard Arkansas stones feature a uniform consistency, showcasing gray, white, yellow, brown, and occasionally pink hues in beautiful, translucent gradients.